Online Etymology Dictionary

tutelary: 1610s, from Latin tutelarius "a guardian," from tutela "protection, watching" (see tutor).
tutor (n.): late 14c., "guardian, custodian," from Old French tutour "guardian, private teacher," from Latin tutorem (nominative tutor) "guardian, watcher," from tutus, variant past participle of tueri "watch over," of unknown origin. Specific sense of "senior boy appointed to help a junior in his studies" is recorded from 1680s.
tutor (v.): 1590s, from tutor (n.). Related: Tutored; tutoring.
tutorial (adj.): 1742, from tutor + -al (1). As a noun, attested from 1923.
tutti-frutti: 1834, from Italian tutti frutti "all fruits," from tutti, plural of tutto "all" + frutti, plural of frutto "fruit."
tutu (n.): ballet skirt, 1910, from French tutu, alteration of cucu, infantile reduplication of cul "bottom, backside."
tux (n.): 1922, colloquial shortening of tuxedo.
tuxedo: man's evening dress for semiformal occasions, 1889, named for Tuxedo Park, N.Y., site of a country club where it first was worn in 1886. The name is an attractive subject for elaborate speculation, e.g.:
The Wolf tribe in New York was called in scorn by other Algonquians tuksit: round foot, implying that they easily fell down in surrender. In their region thus came the names Tuxedo and Tuxedo Lake, which were acquired by the Griswold family in payment of a debt. There the family established the exclusive Tuxedo Club, and there in the late 1880s Griswold Lorillard first appeared in a dinner jacket without tails, a tuxedo. By a twist of slang, one may now refer to a man in a tuxedo as a 'wolf. [Joseph T. Shipley, "The Origins of English Words," 1984]
But in another version of the story, p'tuksit was the Algonquian word for "wolf," the animal, perhaps from the shape of its paws. The authoritative Bright, however, says the tribe's name probably is originally a place name, perhaps Munsee Delaware (Algonquian) p'tuck-sepo "crooked river." Short form tux is attested from 1922.
TV: 1948, shortened form of television (q.v.). TV dinner (1954) is a proprietary name registered by Swanson & Sons, Omaha, Nebraska, U.S.
TWA: formed May 16, 1928, as Transcontinental Air Transport, merged 1930 with Western Air Express to form Transcontinental and Western Air, Inc. (TWA). Name changed to Trans World Airlines 1950, but the moniker remained the same. Last remnants bought out by rival American Airlines in April 2001.
twaddle (n.): "silly talk," 1782, probably from twattle (1550s), of obscure origin.
twain: Old English twegen (masc.) "two" (masc. nominative and accusative), from Proto-Germanic *twa- (see two). The word outlasted the breakdown of gender in Middle English and survived as a secondary form of two, especially in cases where the numeral follows a noun. Its continuation into modern times was aided by its use in KJV and the Marriage Service, in poetry (where it is a useful rhyme word), and in oral use where it is necessary to be clear that two and not to or too is meant.
twang (n.): 1550s, of imitative origin. Originally of bows and strings; extension to "a nasal vocal sound" is first recorded 1660s. The verb is first attested 1540s. Related: Twanged; twanging.
twangy (adj.): 1887, from twang (n.) + -y (2). Related: Twangily; twanginess.
twat (n.): 1650s, of unknown origin. A general term of abuse since 1920s.
The T-word occupies a special niche in literary history, however, thanks to a horrible mistake by Robert Browning, who included it in 'Pippa Passes' (1841) without knowing its true meaning. 'The owls and bats,/Cowls and twats,/Monks and nuns,/In a cloister's moods.' Poor Robert! He had been misled into thinking the word meant 'hat' by its appearance in 'Vanity of Vanities,' a poem of 1660, containing the treacherous lines: 'They'd talk't of his having a Cardinalls Hat,/They'd send him as soon an Old Nuns Twat.' (There is a lesson here about not using words unless one is very sure of their meaning.) [Hugh Rawson, "Wicked Words," 1989]
tweak (v.): "pinch, pluck, twist," usually to the nose, probably from Old English twiccian "to pluck," of obscure origin; perhaps related to twitch. Meaning "to make fine adjustments" is attested from 1966. Related: Tweaked; tweaking. The noun in this sense is recorded by 1989.
twee (adj.): "tiny, dainty, miniature," 1905, from childish pronunciation of sweet.
tweed (n.): 1847 (perhaps as early as 1831), a trade name said to have developed from a misreading (supposedly by London hatter James Locke) of tweel, Scottish variant of twill, possibly influenced by the river Tweed in Scotland.
tweedledum (n.): paired with tweedledee to signify two things or persons nearly alike, differing in name, 1725, coined by English poet John Byrom (1692-1767) in his satire "On the Feud Between Handel and Bononcini," a couple of competing musicians, from tweedle "to sing, to whistle" (1680s), of imitative origin. The -dum and -dee perhaps suggest low and high sounds respectively.
tweedy (adj.): "characteristic of the country or suburban set," 1912, from tweed + -y (2). Related: Tweediness.
tween (prep.): c.1300 as an abbreviation of between. As a noun meaning "child nearing puberty" (approximately ages 9 to 12), attested by 1988, in this case by influence of teen. Related: Tweens.
tweet (n.): 1845, imitative of the sound made by a small bird. As a verb by 1872. Related: Tweeted; tweeting. As the word for what one does on the Twitter microblogging service, by 2007.
tweeter (n.): "loudspeaker for high frequencies," 1934, agent noun from tweet.
tweeze (v.): "to pluck with tweezers," 1932, back-formation from tweezers. Related: Tweezed; tweezing.
tweezers (n.): 1650s, extended from tweezes, plural of tweeze "case for tweezers" (1620s), a shortening of etweese, considered as plural of etwee (1610s) "a small case," from French étui "small case" (see etui). Sense transferred from the case to the implement inside it.
twelfth (adj.): Old English twelfta, cognate with Old Norse tolfti, Old Frisian twelefta, Old High German zwelifto, German zwölfte (see twelve).

Old English twelftan niht "Twelfth Night," the eve of Epiphany, which comes twelve days after Christmas, formerly was a time of merrymaking.
twelve: Old English twelf, literally "two left" (over ten), from Proto-Germanic *twa-lif-, a compound of the root of two + *lif-, root of the verb leave (see eleven). Cf. Old Saxon twelif, Old Norse tolf, Old Frisian twelef, Middle Dutch twalef, Dutch twaalf, Old High German zwelif, German zwölf, Gothic twalif. Outside Germanic, an analogous formation is Lithuanian dvylika, with second element -lika "left over."
twenties (n.): 1829 as the years of someone's life between 20 and 29; 1830 as a decade of years in a given century. See twenty.
twentieth: Old English twentigoða; see twenty + -th.
twenty (n.): Old English twentig "group of twenty," from twegen "two" (see two) + -tig "group of ten" (see -ty (1)). Cognate with Old Frisian twintich, Dutch twintig, Old High German zweinzug, German zwanzig. Gothic twai tigjus is even more transparent: literally "two tens."

The card game twenty-one (1790) is from French vingt-et-un (1781). Twenty-twenty hindsight is first recorded 1962, a figurative use of the Snellen fraction for normal visual acuity, expressed in feet. The guessing game of twenty questions is recorded from 1786. The Twentieth Century Limited was an express train from New York to Chicago 1902-1967.
twerp (n.): of unknown origin; the "Dictionary of American Slang" gives a first reference of 1874 (but without citation), which, if correct, would rule out the usual theory that it is from the proper name of T.W. Earp, a student at Oxford c.1911, who kindled wrath "in the hearts of the rugger-playing stalwarts at Oxford, when he was president of the Union, by being the last, most charming, and wittiest of the 'decadents.' " [Rawson]
twi-: word-forming element meaning "two," Old English twi-, prefix meaning "two, in two ways, twice, double," from Proto-Germanic *twi- (cf. Old Frisian twi-, Old Norse tvi-, Dutch twee-, Old High German zwi-, German zwei-), from PIE *dwis (cf. Sanskrit dvi-, Greek di-, Old Latin dvi-, Latin bi-, Lithuanian dvi-), from *dwo "two" (see two). Cognate with bi-. Older instances of it include Middle English twinter "two years old" (c.1400, of cattle, sheep, etc.), reduced from Old English twi-wintre, and Old English twispræc "double or deceitful speech."
twice (adv.): late Old English twiga, twigea "two times" (cognate with Old Frisian twia, Old Saxon tuuio) + adverbial genitive ending -es.
twiddle (v.): 1540s, "to trifle," of unknown origin; of the fingers, first recorded 1670s. Figurative phrase twiddle one's thumbs "have nothing to do" is recorded from 1846; to twirl one's thumbs in the same sense is recorded from 1816. Related: Twiddled; twiddling.
twig (n.): Old English twigge, from Proto-Germanic *twigan (cf. Middle Dutch twijch, Dutch twijg, Old High German zwig, German Zweig "branch, twig"), from the root of twi- (see twin), here meaning "forked" (as in Old English twisel "fork, point of division").
twiggy (adj.): "slender," 1560s, from twig + -y (2). The famous 1960s English model was born Lesley Hornby (1949).
twilight (n.): late 14c. (twilighting), a compound of twi- + light (n.) Cognate with Dutch tweelicht (16c.), German zwielicht. Exact connotation of twi- in this word is unclear, but it appears to refer to "half" light, rather than the fact that twilight occurs twice a day. Cf. also Sanskrit samdhya "twilight," literally "a holding together, junction," Middle High German zwischerliecht, literally "tweenlight." Originally and most commonly in English with reference to evening twilight but occasionally used of morning twilight (a sense first attested mid-15c.). Figurative extension is first recorded c.1600.
twill (n.): "cloth woven in parallel diagonal lines," early 14c., Scottish and northern English variant of Middle English twile, from Old English twili "woven with double thread, twilled," formed on model of Latin bilix "with a double thread" (with Old English twi- substituted for cognate Latin bi-), from Latin licium "thread," of uncertain origin.
twin (adj.): Old English twinn "consisting of two, twofold, double," probably ultimately from Proto-Germanic *twinjaz (cf. Old Norse tvinnr, Old Danish tvinling, Dutch tweeling, German zwillung), from PIE *dwisno- (cf. Latin bini "two each," Lithuanian dvynu "twins"), from *dwi- "double," from root *dwo- "two" (see two). The verb meaning "to combine two things closely" is recorded from late 14c. The noun developed from Old English getwinn "double."
twine (n.): Old English twin "double thread," from Proto-Germanic *twizna- (cf. Dutch twijn, Low German twern, German zwirn "twine, thread"), from the same root as twin (q.v.). The verb meaning "to twist strands together to form twine" is recorded from late 13c.; sense of "to twist around something" (as twine does) is recorded from c.1300. Related: Twined; twining.
twinge (n.): 1540s, "a pinch," from obsolete verb twinge "to pinch, tweak," from Old English twengan "to pinch," of uncertain origin. Meaning "sharp, sudden pain" is recorded from c.1600. Figurative sense (with reference to shame, remorse, etc.) is recorded from 1620s.
twink (n.): c.1400, "a winking of the eye," also "a twinkle" (1830), from twinkle. Meaning "young sexually attractive person" is recorded from 1963, probably from Twinkies (see Twinkie); but cf. 1920s-30s British homosexual slang twank in a similar sense.
Twinkie (n.): snack food, supposedly invented and named 1930 by Jimmy Dewar, baker for the Chicago branch of Continental Baking Co. (later Hostess); said to have been inspired by twinkle.
twinkle (v.): Old English twinclian, frequentative of twincan "to wink, blink;" related to Middle High German zwinken, German zwinkern, and probably somehow imitative. The noun is recorded from 1540s. Related: Twinkled; twinkling. Phrase in the twinkling of an eye is attested from c.1300.
twirl: 1590s (n. and v.), of uncertain origin, possibly connected with Old English þwirl "a stirrer." Or else a blend of twist and whirl. Related: Twirled; twirling.
twist (n.): mid-14c., "flat part of a hinge," probably from Old English -twist (in mæsttwist "mast rope, stay;" candeltwist "wick"), from Proto-Germanic *twis-, from root of two. Original senses suggest "dividing in two" (cf. cognate Old Norse tvistra "to divide, separate," Gothic twis- "in two, asunder," Dutch twist, German zwist "quarrel, discord," though these senes have no equivalent in English), but later ones are of "combining two into one," hence the original sense of the word may be "rope made of two strands."

Meaning "thread or cord composed of two or more fibers" is recorded from 1550s. Meaning "act or action of turning on an axis" is attested from 1570s. Sense of "beverage consisting of two or more liquors" is first attested c.1700. Meaning "thick cord of tobacco" is from 1791. Meaning "curled piece of lemon, etc., used to flavor a drink" is recorded from 1958. Sense of "unexpected plot development" is from 1941.

The popular rock 'n' roll dance craze is from 1961, but twist was used to describe popular dances in 1894 and again in the 1920s. To get one's knickers in a twist "be unduly agitated" is British slang first attested 1971.
twist (v.): early 14c. (implied in past tense form twaste), "to wring," from the source of twist (n.). Sense of "to spin two or more strands of yarn into thread" is attested from late 15c. Meaning "to move in a winding fashion" is recorded from 1630s. To twist the lion's tail was U.S. slang (1895) for "to provoke British feeling." Related: Twisted; twisting.
twisted (adj.): "perverted, mentally strange," 1900, from twist (n.) in a sense of "mental peculiarity, perversion" first attested 1811.
twister (n.): 1570s, "one who spins thread," agent noun from twist (v.). Meaning "tornado" is attested from 1881, American English.
twisty (adj.): "attractively feminine," 1970s slang, is from twist "girl" (1928), apparently from rhyming slang twist and twirl (1924).