Online Etymology Dictionary

trunnion (n.): "either of two round projections of a cannon," 1620s, from French trognon "core of fruit, stump, tree trunk," from Middle French troignon (14c.), probably from Latin truncus (see trunk (n.1)).
truss (n.): c. 1200, "collection of things bound together," from Old French trousse, torse "parcel, package, bundle," of uncertain origin, perhaps from Vulgar Latin *torciare "to twist," from Late Latin torquere (see torque (n.)). Meaning "surgical appliance to support a rupture, etc." first attested 1540s. Sense of "framework for supporting a roof or bridge" is first recorded 1650s.
truss (v.): c. 1200, "to load, load up," from Anglo-French trusser, Old French trusser, torser "to load, fill, pack, fasten" (11c.), from Old French trousse, torse (see truss (n.)). Related: Trussed; trussing.
trust (n.): c. 1200, "reliance on the veracity, integrity, or other virtues of someone or something; religious faith," from Old Norse traust "help, confidence, protection, support," from Proto-Germanic abstract noun *traustam (source also of Old Frisian trast, Dutch troost "comfort, consolation," Old High German trost "trust, fidelity," German Trost "comfort, consolation," Gothic trausti "agreement, alliance"), from Proto-Germanic *treuwaz-, source of Old English treowian "to believe, trust," and treowe "faithful, trusty" (see true (adj.)).

from c. 1300 as "reliability, trustworthiness; trustiness, fidelity, faithfulness;" from late 14c. as "confident expectation" and "that on which one relies." From early 15c. in legal sense of "confidence placed in a one who holds or enjoys the use of property entrusted to him by its legal owner;" mid-15c. as "condition of being legally entrusted." Meaning "businesses organized to reduce competition" is recorded from 1877. Trust-buster is recorded from 1903.
trust (v.): c. 1200, from Old Norse treysta "to trust, rely on, make strong and safe," from traust (see trust (n.)). Related: Trusted; trusting.
trustee (n.): "person who is responsible for the property of another," 1640s, from trust (v.) + -ee.
trustful (adj.): 1570s, "trustworthy," from trust (n.) + -ful. Meaning "trusting" attested from 1832. Related: Trustfully, trustfulness.
trustworthy (adj.): 1791, from trust (n.) + worthy. Related: Trustworthiness.
trusty (adj.): early 13c., "trusting," from trust (n.) + -y (2). Old English expressed this idea by treowful. Meaning "reliable, to be counted on" is from early 14c. The noun meaning "trustworthy person" is from 1570s; specifically as "a prisoner granted special privileges as reward for good conduct" by 1855.
truth (n.): Old English triewð (West Saxon), treowð (Mercian) "faith, faithfulness, fidelity, loyalty; veracity, quality of being true; pledge, covenant," from triewe, treowe "faithful" (see true (adj.)), with Proto-Germanic abstract noun suffix *-itho (see -th (2)).

Sense of "something that is true" is first recorded mid-14c. Meaning "accuracy, correctness" is from 1560s. English and most other IE languages do not have a primary verb for for "speak the truth," as a contrast to lie (v.). Truth squad in U.S. political sense first attested in the 1952 U.S. presidential election campaign.
At midweek the Republican campaign was bolstered by an innovation--the "truth squad" ..., a team of senators who trailed whistle-stopping Harry Truman to field what they denounced as his wild pitches. ["Life," Oct. 13, 1952]

Let [Truth] and Falsehood grapple; who ever knew Truth put to the worse, in a free and open encounter. [Milton, "Areopagitica," 1644]
truthful (adj.): "habitually speaking truth," 1590s, from truth + -ful. Related: Truthfully; truthfulness.
truthiness (n.): "act or quality of preferring concepts or facts one wishes to be true, rather than those known to be true," a catch word popularized in this sense by U.S. comedian Stephen Colbert (b.1964), declared by American Dialect Society to be "2005 Word of the Year." It was used in 1832 in a sense "habit of telling the truth," from truthy "characterized by truth" (1800), from truth (n.) + -y (2).
try (v.): c. 1300, "examine judiciously, discover by evaluation, test;" mid-14c., "sit in judgment of," also "attempt to do," from Anglo-French trier (13c.), from Old French trier "to pick out, cull" (12c.), from Gallo-Roman *triare, of unknown origin. The ground sense is "separate out (the good) by examination." Sense of "subject to some strain" (of patience, endurance, etc.) is recorded from 1530s. To try on "test the fit of a garment" is from 1690s; to try (something) on for size in the figurative sense is recorded by 1946. Try and instead of try to is recorded from 1680s.
try (n.): late 15c., "screen for sifting," from try (v.). From 1832 as "an effort, an attempt."
trying (adj.): "distressing," 1718, present-participle adjective from try (v.). Related: Tryingly.
tryout (n.): also try-out, by 1900, from phrase to try out "to examine, test," attested by 1785.
trypsin (n.): chief digestive enzyme of pancreatic juice, 1876, coined 1874 by German physiologist Wilhelm Friedrich Kühne (1837-1900), apparently from Greek tripsis "rubbing, friction" (from tribein "to rub, rub down, wear away," from PIE root *tere- (1) "to rub, turn, twist" (see throw (v.)) + chemical suffix -in (2). Said to be so called because it first was obtained (in 1862) by rubbing the pancreas with glycerin.
tryptic (adj.): 1877, from trypsin + -ic (compare pepsin/peptic).
tryptophan (n.): also tryptophane, complex amino acid, 1890, coined in German (1876) from trypto-, taken as a comb. form of tryptic "by trypsin" (see trypsin) + Greek phainein "to appear" (see phantasm).
tryst (n.): late 14c., "appointment to meet at a certain time and place," from Old French tristre "waiting place, appointed station in hunting," probably from a Scandinavian source such as Old Norse treysta "to trust, make firm" (see trust (v.)). The notion would be "place one waits trustingly." As a verb, late 14c. Related: Trysting.
tsar (n.): 1660s, the more correct Latinization of Russian czar, from prehistoric Slavic *tsesar, from a Germanic source, ultimately from Latin Caesar. See czar. Related: Tsardom; tsarevich; tsarina; tsarevna.
tsetse (n.): fly of tropical Africa, 1849, probably via South African Dutch, from a Bantu language (compare Setswana tsetse, Luyia tsiisi "flies").
tsk: sound expressing commiseration or disapproval, 1947; as a verb, tsk-tsk is recorded from 1967.
Tso: in Chinese restaurant dishes, a reference to General Tso Tsungtang (1812-1885), military leader during the late Qing dynasty who crushed the Taiping rebels in four provinces. The chicken dish that bears his name (for no apparent reason) in Chinese restaurants apparently is modified from a traditional Hunan chung ton gai and may have been named for the general c. 1972 by a chef in New York City during the time Hunan cuisine first became popular among Americans.
tsunami (n.): 1896, in reference to the one that struck Japan that year on June 15, from Japanese tsunami, from tsu "harbor" + nami "waves."
tu quoque: Latin, literally "thou also" (or, in modern vernacular, "so are you!"); an argument which consists in retorting accusations.
tuatara (n.): New Zealand lizard, 1844, from Maori, from tua "on the back" + tara "spine."
Tuatha de Danann: 1680s, from Irish Tuatha dé Danann, literally "the people of Danann," from plural of tuath (see Teutonic) + Danann, apparently originally an oblique case of Danu, mother of the gods.
tub (n.): "open wooden vessel made of staves," late 14c., from Middle Low German, Middle Dutch, or Middle Flemish tubbe, of uncertain origin. Related to Old High German zubar "vessel with two handles, wine vessel," German Zuber. Considered to be unrelated to Latin tubus (see tube (n.)); one theory connects it to the root of two based on the number of handles. Also 17c. slang for "pulpit;" hence tub-thumper (1660s) "speaker or preacher who thumps the pulpit for emphasis."
tuba (n.): 1852 in reference to a modern, large, low-pitched brass musical instrument, from French tuba, from Latin tuba (plural tubae) "straight bronze war trumpet" (as opposed to the crooked bucina), related to tubus (see tube (n.)).
tubby (adj.): "shaped like a tub, corpulent," 1835, from tub + -y (2). The noun meaning "a fat person" is attested from 1891. Related: Tubbily; tubbiness.
tube (n.): 1610s, from Middle French tube (15c.), from Latin tubus "tube, pipe," of unknown origin. The London subway was christened the Twopenny Tube (H.D. Browne, in the "Londoner" of June 30, 1900) before it even opened; tube for "cylindrical railway tunnel" is attested from 1847. The meaning "TV as a medium" is from 1959, short for cathode ray tube or picture tube. Tube top as a women's clothing style is attested from 1972. Tube steak is attested from 1963 as "frankfurter," slang meaning "penis" is recorded by mid-1980s.
tuber (n.): "thick underground stem," 1660s, from Latin tuber "edible root, truffle; lump, bump, swelling," from PIE *tubh-, from root *teue- (2) "to swell" (see thigh).
tubercle (n.): 1570s, from Latin tuberculum "a small swelling," diminutive of tuber "lump" (see tuber).
tubercular (adj.): 1799, "characterized by tubers," from Latin tuberculum (see tubercule) + -ar. From 1898 as "having tuberculosis."
tuberculosis (n.): 1860, "disease characterized by tubercules," a medical Latin hybrid, from Latin tuberculum "small swelling, pimple," diminutive of tuber "lump" (see tuber) + -osis, a suffix of Greek origin. So called in reference to the tubercules which form in the lungs. Originally in reference to any disease characterized by tubercules; since the discovery in 1882 of the tubercule bacillus by German bacteriologist Robert Koch (1843-1910) restricted to disease caused by this. Abbreviation T.B. attested from 1912.
tuberculous (adj.): "characterized by tubers," 1747, from Latin tuberculum (see tubercule) + -ous.
tubing (n.): recreational pastime of riding a river on a truck tire inner tube, 1975; see tube (n.).
tubular (adj.): 1670s, "having the form of a tube or pipe," from Latin tubulus "a small pipe" (see tube) + -ar. Teen slang sense attested by 1982, Valspeak, apparently from surfers' use of tube as slang for a hollow, curling wave, ideal for riding (1962).
tuck (v.): late 14c., "to pull or gather up," earlier "to pluck, stretch" (implied in tucker "one who finishes clothes by stretching them on tenters, late 13c. as a surname), probably from Middle Low German or Middle Dutch tucken "pull up, draw up, tug" (cognate with Old English tucian "mistreat, torment," and related to Old English togian "to pull," German zucken; see tow (v.)). Sense of "thrust into a snug place" is first recorded 1580s. Slang meaning "to consume, swallow, put into one's stomach" is recorded from 1784. Related: Tucked; tucking.
tuck (n.): late 14c., "flattened fold in clothing, pleat," from tuck (v.). As a folded-up diving position, from 1951.
tuckahoe (n.): edible plant root of eastern U.S., 1610s, American English, from Powhatan (Algonquian) tockawhouge (compare Mohegan tquogh, Shawnee tukwhah), perhaps related to Cree (Algonquian) pitikwaw "made round." From early 19c. a name applied in Virginia to those east of the Blue Ridge Mountains by the settlers west of them, who called themselves Cohees.
tucker (n.): "piece of lace worn around the neck," 1680s, agent noun from tuck (v.). In Middle English tukere was "one who dresses or finishes cloth," hence the surname.
tucker (v.): "to tire, weary," 1833, New England slang, of uncertain origin, perhaps from tucked (past participle of tuck (v.)), which had, in reference to dogs, a slang sense of "exhausted, underfed." Especially with out. Related: Tuckered; tuckering.
Tucson: city in Arizona, U.S.A., from Spanish Tucson, from O'odham (Piman) cukson "black base," from cuk "black" + son "base."
tude (n.): teenager slang shortening of attitude, 1970s.
Tudor: 1779 in reference to the English royal family, from Welsh surname Tewdwr, used of the line of English sovereigns from Henry VII to Elizabeth I, descended from Owen Tudor, who married Catherine, widowed queen of Henry V. Applied from 1815 to a style of architecture prevalent during these reigns. The name is the Welsh form of Theodore.
Tuesday (n.): third day of the week, Old English tiwesdæg, from Tiwes, genitive of Tiw "Tiu," from Proto-Germanic *Tiwaz "god of the sky," the original supreme deity of ancient Germanic mythology, differentiated specifically as Tiu, ancient Germanic god of war, from PIE *deiwos "god," from root *dyeu- "to shine" (see diurnal). Compare Old Frisian tiesdei, Old Norse tysdagr, Swedish tisdag, Old High German ziestag.

The day name (second element dæg, see day) is a translation of Latin dies Martis (source of Italian martedi, French Mardi) "Day of Mars," from the Roman god of war, who was identified with Germanic Tiw (though etymologically Tiw is related to Zeus), itself a loan-translation of Greek Areos hemera. In cognate German Dienstag and Dutch Dinsdag, the first element would appear to be Germanic ding, þing "public assembly," but it is now thought to be from Thinxus, one of the names of the war-god in Latin inscriptions.
tufa (n.): type of porous rock, 1770, from Italian tufa "tufa, porous rock," probably from Latin tufus, tophus "loose, porous volcanic rock," said to be an Oscan-Umbrian loan-word. Related: Tufaceous.
tuff (adj.): advertiser's spelling of tough (adj.), attested by 1940.