1816, "underhand" (in reference to a style of throwing), from under + arm (n.1). First attested 1908 in dressmaking sense of "seams on the lower half of the arm-hole;" as a euphemism for armpit, it is attested from 1930s, popularized by advertisers.ETD underarm (adj.).2

underbelly (n.)

c. 1600, from under + belly (n.). In figurative sense of "most vulnerable part" it is recorded from Churchill's 1942 speech. Sometimes used erroneously or euphemistically in sense of "seamy or sordid part" of anything.ETD underbelly (n.).2

underbid (v.)

1610s, from under + bid (v.). Related: Underbidding.ETD underbid (v.).2

underbred (adj.)

"of inferior breeding, vulgar," 1640s, from under + past participle of breed (v.). Of animals, "not pure bred," attested from 1890.ETD underbred (adj.).2

underbrush (n.)

"shrub and small trees in a forest," 1775, from under + brush (n.2). Originally American English; compare undergrowth, attested in the same sense from 1600.ETD underbrush (n.).2

undercarriage (n.)

1794, from under + carriage (n.). Meaning "landing gear of an aircraft" is recorded from 1911.ETD undercarriage (n.).2

undercharge (v.)

1630s, from under + charge (v.).ETD undercharge (v.).2

underclass (n.)

"subordinate social class," 1894, from under (adj.) + class (n.). A loan-translation of Swedish underklass.ETD underclass (n.).2

underclassman (n.)

"sophomore or freshman," 1869, American English, from under (adj.) + class (n.) in the school form sense + man (n.).ETD underclassman (n.).2

undercover (adj.)

1854, "sheltered," from under + cover (n.). Sense of "operating secretly" attested from 1920.ETD undercover (adj.).2

undercroft (n.)

"crypt of a church; underground vault," late 14c., from under + croft.ETD undercroft (n.).2

undercurrent (n.)

1660s, "stream of water or air flowing beneath the surface or beneath another current," a hybrid formed from under + current (n.). The figurative sense of "suppressed or underlying character" is attested from 1817.ETD undercurrent (n.).2

undercut (v.)

late 14c., "to cut down or off," from under + cut (v.). In the commercial sense of "sell at lower prices" (or work at lower wages) it is first attested 1884. Figurative sense of "render unstable, undermine" is recorded from 1955, from earlier literal meaning "cut so as to leave the upper portion larger than the lower" (1874).ETD undercut (v.).2

underdeveloped (adj.)

1892, in photography, from under + past participle of develop (v.). In reference to countries or regions, recorded from 1949.ETD underdeveloped (adj.).2

underdog (n.)

"the beaten dog in a fight," 1887, from under + dog (n.). Compare top dog "dominant person in a situation or hierarchy" (see top (adj.)). Its opposite, overdog, is attested by 1908.ETD underdog (n.).2

underdone (adj.)

1680s, in reference to cooked meat, from under + done. Old English underdon (v.), Middle English underdo meant "to put under, to subject, subjugate."ETD underdone (adj.).2

underdressed (adj.)

also under-dressed, "too plainly dressed," 1759, from under (adv.) + past participle of dress (v.).ETD underdressed (adj.).2

under-employed (adj.)

1908, "not used to optimum capacity," originally in reference to working persons, from under + past participle of employ (v.).ETD under-employed (adj.).2

under-employment (n.)

also underemployment, 1909, from under + employment.ETD under-employment (n.).2

underestimate (v.)

1812, "to estimate at too low an amount," from under + estimate (v.). Meaning "to rank too low, undervalue" is recorded from 1850. Related: Underestimated; underestimating.ETD underestimate (v.).2

underexposed (adj.)

1861, in photography, from under + past participle of expose (v.).ETD underexposed (adj.).2

underfeed (v.)

1650s, from under + feed (v.). Related: Underfed; underfeeding.ETD underfeed (v.).2

underfoot (adv.)

c. 1200, underfot "under the feet," from under + foot (n.). Compare similarly formed Middle Dutch ondervoete. As an adjective, attested from 1590s; in reference to persons, "continually in the way," it is recorded from 1891. Middle English under fot meant "vanquished, overcome."ETD underfoot (adv.).2

undergarment (n.)

1520s, from under + garment (n.).ETD undergarment (n.).2

undergird (v.)

1520s, from under + gird (v.). Related: Undergirded; undergirding.ETD undergird (v.).2

undergo (v.)

Old English undergan "obtain, get; undertake," from under + gan (see go (v.)). Compare similarly formed Middle Dutch ondergaen, Old High German untarkun, German untergehen, Danish undergaa. Sense of "submit to, endure" is attested from c. 1300. Meaning "to pass through" (an alteration, etc.) is attested from 1630s. Related: Undergone; underwent.ETD undergo (v.).2

undergrad (n.)

short for undergraduate, 1827.ETD undergrad (n.).2

undergraduate (n.)

1620s, a hybrid formed from under + graduate (n.). British used fem. form undergraduette in 1920s-30s. As an adjective, in the school sense, from 1680s.ETD undergraduate (n.).2

underground (adv.)

1570s, "below the surface," from under + ground (n.). As an adjective, attested from c. 1600; figurative sense of "hidden, secret" is attested from 1630s; adjectival meaning "subculture" is from 1953, from adjectival use in reference to World War II resistance movements against German occupation, on analogy of the dominant culture and the Nazis. Noun sense of "underground railway" is from 1887 (shortened from phrase underground railway, itself attested from 1834).ETD underground (adv.).2

Underground Railroad (n.)

"network of U.S. anti-slavery activists helping runaways elude capture," attested from 1847, but said to date from 1831 and to have been coined in jest by bewildered trackers after their slaves vanished without a trace. Originally mostly the term for escape networks in the (then) western states of the U.S.ETD Underground Railroad (n.).2

undergrowth (n.)

"shrubs or small trees growing amid larger ones," c. 1600, from under + growth.ETD undergrowth (n.).2

underhanded (adj.)

in reference to a throw, etc., "performed or done with the knuckles turned under," 1807, from under + hand (n.). Compare underhand. As "in secret," from 1825; as "with too few people," from 1834. Related: Underhandedly; underhandedness.ETD underhanded (adj.).2

underhand (adv.)

mid-14c., "by secret means, stealthily, in a surreptitious manner," from under + hand (n.). Perhaps the notion is of the hand turned over (thus concealing what it holds). Compare Middle Dutch onderhanden "by degrees, slowly," Dutch onderhandsch "secret, private." The adjective is attested from 1540s. Old English under hand meant "in subjection, in (one's) control or power."ETD underhand (adv.).2

underling (n.)

late Old English, "one who owes allegiance to a sovereign or ruler," from under + diminutive suffix -ling. Middle English had also overling "a superior, one who is superior in a hierarchy" (mid-14c.).ETD underling (n.).2

underlay (v.)

Old English under lecgan "to support by placing something beneath;" see under + lay (v.). Related: Underlaid; underlaying. Compare similarly formed Old High German Related: untarleccan, German unterlegen.ETD underlay (v.).2

underlie (v.)

Old English under licgan "to be subordinate to, to submit to;" see under + lie (v.2). Meaning "to lie under or beneath" is attested from c. 1600; figurative sense of "to be the basis of" is attested from 1852 (implied in underlying). Similar formation in Old High German untarliggan; German unterliegen.ETD underlie (v.).2

underlying (adj.)

1610s, present-participle adjective from underlie.ETD underlying (adj.).2

underline (v.)

1721, "to mark underneath or below with a line," from under + line (v.). Similar formation in Dutch onderlijnen. Related: Underlined; underlining. The noun is attested from 1888.ETD underline (v.).2

undermine (v.)

c. 1300, undermyne, "render unstable by digging at the foundation," from under + mine (v.1) "dig." The figurative sense "injure by invisible, secret, or dishonorable means" is attested from early 15c. Similar formation in Dutch ondermijnen, Danish underminere, German unterminiren. The Old English verb was underdelfan. Related: Undermined; undermining.ETD undermine (v.).2

undern (n.)

an obsolete Old English and Middle English word for "morning;" in Old English originally "third hour of the day; 9 a.m." (corresponding to tierce). Hence underngeweorc, undernmete "breakfast." Common Germanic: Old Frisian unden, Old Saxon undorn, Middle Dutch onderen, Old High German untarn, Old Norse undorn; of uncertain origin. By extension, "period from 9 a.m. to noon;" but from 13c. shifting to "midday, noon" (as in undern-mete "lunch," 14c.); and by late 15c. to "late afternoon or early evening."ETD undern (n.).2

underneath (adv.)

Old English underneoðan, from under + neoðan "below" (see beneath).ETD underneath (adv.).2

undernourished (adj.)

also under-nourished, 1820, from under + past participle of nourish (v.).ETD undernourished (adj.).2

underpants (n.)

1931, from under + pants. Drove out drawers, knickers in this sense in American English.ETD underpants (n.).2

underpay (v.)

1817, from under + pay (v.). Related: underpaid (1762); underpaying.ETD underpay (v.).2

underpass (n.)

1904, American English, from under + pass (n.).ETD underpass (n.).2

underpinning (n.)

late 15c., "action of supporting or strengthening from beneath," from under + present participle of pin (v.). Figurative sense of "prop, support" is recorded from 1580s.ETD underpinning (n.).2

underpin (v.)

"support or prop," 1520s (figurative); 1530s (literal), from under + pin (v.). Related: Underpinned; underpinning.ETD underpin (v.).2

underprivileged (adj.)

1896, from under + past participle of privilege (v.). Noun use (short for underprivileged persons) is attested from 1935.ETD underprivileged (adj.).2

underrate (v.)

also under-rate, 1640s, "to esteem at too little worth," from under + rate (v.). Related: Underrated; underrating.ETD underrate (v.).2

underscore (v.)

1771, "to draw a line under," from under + score (v.). The figurative sense of "to emphasize" is attested from 1891. Noun meaning "a line drawn below (something)" is recorded from 1901.ETD underscore (v.).2

undersea (adj.)

1610s, from under + sea.ETD undersea (adj.).2

underserve (v.)

"to serve insufficiently," 1710, from under + serve (v.). Related: Underserved; underserving.ETD underserve (v.).2

undershirt (n.)

1640s, from under (adj.) + shirt (n.). Similar formation in North Frisian onnersjürt, Danish underskjorte. Old English had undersyrc (see sark (n.)).ETD undershirt (n.).2

undershoot (v.)

1660s, "to shoot too low," from under + shoot (v.). In reference to aircraft or pilots, recorded from 1918. Undershot as a type of water wheel is recorded from c. 1600.ETD undershoot (v.).2

underside (n.)

1680s, from under (adj.) + side (n.). Similar formation in Dutch onderzijde, Danish underside, German unterseite.ETD underside (n.).2

undersign (v.)

1570s, from under + sign (v.). Related: Undersigned; undersigning.ETD undersign (v.).2

understated (adj.)

1939, of clothing, fashions, writing, etc., figurative use of the past participle of understate (v.).ETD understated (adj.).2

understate (v.)

1781, from under + state (v.). Related: Understated; understating.ETD understate (v.).2

understandable (adj.)

late 14c., "able to understand;" late 15c., "able to be understood," from understand + -able. Related: Understandably.ETD understandable (adj.).2

understanding (n.)

Old English understanding "comprehension," verbal noun from understand (v.). Meaning "mutual agreement" is attested from 1803.ETD understanding (n.).2

understand (v.)

Old English understandan "to comprehend, grasp the idea of, receive from a word or words or from a sign the idea it is intended to convey; to view in a certain way," probably literally "stand in the midst of," from under + standan "to stand" (see stand (v.)).ETD understand (v.).2

If this is the meaning, the under is not the usual word meaning "beneath," but from Old English under, from PIE *nter- "between, among" (source also of Sanskrit antar "among, between," Latin inter "between, among," Greek entera "intestines;" see inter-). Related: Understood; understanding.ETD understand (v.).3

That is the suggestion in Barnhart, but other sources regard the "among, between, before, in the presence of" sense of Old English prefix and preposition under as other meanings of the same word. "Among" seems to be the sense in many Old English compounds that resemble understand, such as underniman "to receive," undersecan "examine, investigate, scrutinize" (literally "underseek"), underðencan "consider, change one's mind," underginnan "to begin."ETD understand (v.).4

It also seems to be the sense still in expressions such as under such circumstances. Perhaps the ultimate sense is "be close to;" compare Greek epistamai "I know how, I know," literally "I stand upon."ETD understand (v.).5

Similar formations are found in Old Frisian (understonda), Middle Danish (understande), while other Germanic languages use compounds meaning "stand before" (German verstehen, represented in Old English by forstanden "understand," also "oppose, withstand"). For this concept, most Indo-European languages use figurative extensions of compounds that literally mean "put together," or "separate," or "take, grasp" (see comprehend).ETD understand (v.).6

The range of spellings of understand in Middle English (understont, understounde, unþurstonde, onderstonde, hunderstonde, oundyrston, wonderstande, urdenstonden, etc.) perhaps reflects early confusion over the elements of the compound. Old English oferstandan, Middle English overstonden, literally "over-stand" seem to have been used only in literal senses.ETD understand (v.).7

By mid-14c. as "to take as meant or implied (though not expressed); imply; infer; assume; take for granted." The intransitive sense of "have the use of the intellectual faculties; be an intelligent and conscious being" also is in late Old English. In Middle English also "reflect, muse, be thoughtful; imagine; be suspicious of; pay attention, take note; strive for; plan, intend; conceive (a child)." Also sometimes literal, "to occupy space at a lower level" (late 14c.) and, figuratively, "to submit." For "to stand under" in a physical sense, Old English had undergestandan.ETD understand (v.).8

understatement (n.)

1799, from under + statement.ETD understatement (n.).2

understory (n.)

in reference to forest vegetation, also under-story, 1902, from under + story (n.).ETD understory (n.).2

understudy (v.)

also under-study, 1852, in the theatrical sense "memorize a part so as to be capable of performing on short notice it in the absence of the one to which it is assigned," from under + study (v.). The noun is attested from 1848, translating Italian supplimento.ETD understudy (v.).2

undertake (v.)

c. 1200, "to entrap;" c. 1300, "to set about (to do)," from under + take (v.). Similar formation in French entreprendre "to undertake," from entre "between, among" + prendre "to take." The under in this word may be the same one that also may form the first element of understand. Old English had underniman "to trap, accept" (cognate with Dutch ondernemen, German unternehmen).ETD undertake (v.).2

undertaking (n.)

"enterprise," early 15c., verbal noun from undertake (v.). An Old English word for this was underfangenes.ETD undertaking (n.).2

undertaker (n.)

c. 1400, "a contractor or projecter of any sort," agent noun from undertake (v.). The specialized sense (1690s) emerged from funeral-undertaker.ETD undertaker (n.).2

undertone (n.)

1762, "low or subdued tone," from under + tone (n.). Figurative sense of "undercurrent of feelings, etc.," is attested from 1861.ETD undertone (n.).2

undertow (n.)

1798, from under + tow (n.).ETD undertow (n.).2

underutilize (v.)

also under-utilize, 1949, from under + utilize. Related: Underutilized; underutilizing.ETD underutilize (v.).2

undervalue (v.)

1590s, "to rate as inferior in value" (to), from under + value (v.). Sense of "to estimate or esteem too low" is recorded from 1610s. Meaning "to rate at too low a monetary value" is attested from 1620s. Related: Undervalued; undervaluing.ETD undervalue (v.).2

underway (adv.)

1749, of ships, "having begun to move," from under + way (n.). In reference to projects, activities, etc., it is attested from 1935.ETD underway (adv.).2

underwater (adj.)

1620s, from under + water (n.1). Of mortgages from 2008.ETD underwater (adj.).2

underwear (n.)

"undergarments," 1872, from under + wear (n.). So called because they are worn under one's clothing.ETD underwear (n.).2

underweight (adj.)

1899, from under- + weight.ETD underweight (adj.).2

underwhelm (v.)

1953 (implied in underwhelming), a facetious play on overwhelm, with under. Related: Underwhelmed; underwhelmingly.ETD underwhelm (v.).2

underworld (n.)

c. 1600, "the lower world, Hades, place of departed souls," also "the earth, the world below the skies," as distinguished from heaven; see under + world. Similar formation in German unterwelt, Dutch onderwereld, Danish underverden. The meaning "lower level of society" is attested from 1890; the sense of "criminals and organized crime collectively" is attested from 1900.ETD underworld (n.).2

underwriter (n.)

1610s, "subscriber," agent noun from underwrite (v.). Insurance sense is from 1620s.ETD underwriter (n.).2

underwrite (v.)

Old English underwritan "write at the foot of; subscribe;" see under + write (v.). A loan-translation of Latin subscribere (see subscribe). Used literally at first; modern sense of "to accept the risk of insurance" (1620s) is from notion of signing a marine insurance policy. Meaning "to support by a guarantee of money" is recorded from 1890.ETD underwrite (v.).2

undeserved (adj.)

late 14c., from un- (1) "not" + past participle of deserve (v.). Related: Undeservedly.ETD undeserved (adj.).2

undeserving (adj.)

1540s, from un- (1) "not" + present participle of deserve (v.).ETD undeserving (adj.).2

undesirable (adj.)

1660s, "not to be desired, objectionable," from un- (1) "not" + desirable. The noun meaning "undesirable person or thing" is first attested 1883. Undesired "not asked or invited" is recorded from late 15c.ETD undesirable (adj.).2

undeterred (adj.)

c. 1600, from un- (1) "not" + past participle of deter (v.).ETD undeterred (adj.).2

undetectable (adj.)

1789, from un- (1) "not" + detectable.ETD undetectable (adj.).2

undetected (adj.)

1590s, from un- (1) "not" + past participle of detect (v.).ETD undetected (adj.).2

undetermined (adj.)

mid-15c., from un- (1) "not" + past participle of determine (v.).ETD undetermined (adj.).2

undeveloped (adj.)

1736, from un- (1) "not" + past participle of develop (v.). In reference to film, it is attested from 1939.ETD undeveloped (adj.).2

undeviating (adj.)

1732, from un- (1) "not" + present participle of deviate (v.).ETD undeviating (adj.).2

undies (n.)

1906, diminutive euphemistic abbreviation for women's underwear (or undergarments).ETD undies (n.).2

undying (adj.)

c. 1300, "immortal," from un- (1) "not" + present participle of die (v.). Figurative sense, of feelings, etc., is recorded from c. 1765.ETD undying (adj.).2

undifferentiated (adj.)

1862, from un- (1) "not" + past participle of differentiate (v.).ETD undifferentiated (adj.).2

undigested (adj.)

1520s, from un- (1) "not" + past participle of digest (v.). Figurative sense is recorded from c. 1600.ETD undigested (adj.).2

undignified (adj.)

1680s, of clergy, "not holding a position of dignity," from un- (1) "not" + dignified. Meaning "lacking in dignity of manner" is attested from 1782.ETD undignified (adj.).2

undiluted (adj.)

1756, from un- (1) "not" + past participle of dilute (v.).ETD undiluted (adj.).2

undiminished (adj.)

1580s, from un- (1) "not" + past participle of diminish (v.).ETD undiminished (adj.).2

undine (n.)

female water spirit, 1821, from Modern Latin Undina (1650s), coined by Paracelsus ("De Nymphis") in his alchemical system, from Latin unda "a wave, billow" (from PIE root *wed- (1) "water; wet"). Popularized by German romance "Undine, eine Erzählung" (1811) by Baron F.H.C. La Motte Fouqué. Undinism (1928) was coined by sex researcher Havelock Ellis to describe the fetish for urine (which Ellis had); nowadays it would be called urophilia.ETD undine (n.).2

undisciplined (adj.)

late 14c., "untrained," from un- (1) "not" + past participle of discipline (v.). Similar formation in German undisciplinirt, Swedish odisciplinerad. Specific meaning "not subject to military discipline" is attested from 1718.ETD undisciplined (adj.).2

undisclosed (adj.)

1560s, from un- (1) "not" + past participle of disclose (v.).ETD undisclosed (adj.).2

undiscovered (adj.)

1540s, from un- (1) "not" + past participle of discover (v.).ETD undiscovered (adj.).2

undisguised (adj.)

c. 1500, in reference to things, from un- (1) "not" + past participle of disguise (v.). Of persons, attested from 1670s.ETD undisguised (adj.).2

uncial (adj.) — under-achiever (n.)

undismayed (adj.) — unfrequented (adj.)