Online Etymology Dictionary

W: not in the Roman alphabet, but the Modern English sound it represents is close to the devocalized consonant expressed by Roman -U- or -V-. In Old English, this originally was written -uu-, but by 8c. began to be expressed by the runic character wyn (Kentish wen), which looked like this: ƿ (the character is a late addition to the online font set and doesn't display properly on many computers, so it's something like a combination of lower-case -p- and a reversed -y-). In 11c., Norman scribes introduced -w-, a ligatured doubling of Roman -u- which had been used on the continent for the Germanic "w" sound, and wyn disappeared c. 1300. -W- is not properly a letter in the modern French alphabet, and it is used there only in borrowed foreign words, such as wagon, weekend, Western, whisky, wombat.
W.C. (n.): "lavatory," by 1871, abbreviation of water-closet.
WAC: 1943, American English, acronym from Women's Army Corps, formed 1943.
wack (n.): "crazy person," 1938, back-formation from wacky. Adjective in slang sense of "worthless, stupid," is attested from late 1990s.
wacke (n.): rock resembling sandstone, 1803, from German Wacke, from Middle High German wacke "large stone, rock projecting from the surface of the ground," from Old High German wacko, waggo "gravel, pebble," probably from Old High German wegan "to move." A miner's word, brought into geology by German geologist Abraham Gottlob Werner (1750-1817).
wacko (n.): extended form of wack, by 1971.
wacky (adj.): "crazy, eccentric," 1935, variant of whacky (n.) "fool," late 1800s British slang, probably ultimately from whack "a blow, stroke," from the notion of being whacked on the head one too many times.
wad (n.): early 15c., wadde, "small bunch of fibrous, soft material for padding or stuffing," of uncertain origin, perhaps from Medieval Latin wadda (14c., source also of French ouate, Italian ovate), or Dutch watten (source of German Watte), or Middle English wadmal (c. 1300) "coarse woolen cloth," which seems to be from Old Norse vaðmal "a woolen fabric of Scandinavia," probably from vað "cloth" + mal "measure."

The meaning "something bundled up tightly" (especially paper currency) is from 1778. To shoot (one's) wad "do all one can do" is recorded from 1914. The immediate source of the expression probably is the sense of "disk of cloth used to hold powder and shot in place in a gun." Wad in slang sense of "a load of semen" is attested from 1920s, and the expression now often is felt in this sense. As a suffix, -wad in 1980s joined -bag, -ball, -head in combinations meaning "disgusting or unpleasant person."
wad (v.): 1570s, "put a wad into," from wad (n.). From 1670s as "form into a wad;" 1759 as "pad or stuff with wadding." Related: Wadded; wadding.
wadding (n.): "stuffing," 1620s, verbal noun from wad (v.).
waddle (v.): "to walk with short steps, swaying from side to side; to walk as a duck does," 1590s, frequentative of wade. Related: Waddled; waddling. The noun is recorded from 1690s.
wade (v.): Old English wadan "to go forward, proceed, move, stride, advance" (the modern sense perhaps represented in oferwaden "wade across"), from Proto-Germanic *wadan (source also of Old Norse vaða, Danish vade, Old Frisian wada, Dutch waden, Old High German watan, German waten "to wade"), from PIE root *wadh- (2) "to go," found only in Germanic and Latin (source also of Latin vadere "to go," vadum "shoal, ford," vadare "to wade"). Italian guado, French gué "ford" are Germanic loan-words.

Specifically "walk into or through water" (or any substance which impedes the free motion of limbs) c. 1200. Originally a strong verb (past tense wod, past participle wad); weak since 16c. Figurative sense of "to go into" (action, battle, etc.) is recorded from late 14c. Related: Waded; wading.
Forbade to wade through slaughter to a throne,
And shut the gates of mercy on mankind,

[Gray, "Elegy Written in a Country Churchyard"]
waders (n.): "waterproof high boots," 1841, plural agent noun from wade.
wadi (n.): "watercourse," 1839, from Arabic wadi "seasonal watercourse," prop. participle of wada "it flowed." It forms the Guadal- in Spanish river names.
wae (n.): obsolete or dialectal Scottish form of woe.
wafer (n.): late 14c., "thin cake of paste, generally disk-shaped," from Anglo-French wafre, Old North French waufre "honeycomb, wafer" (Old French gaufre "wafer, waffle"), probably from Frankish *wafel or another Germanic source (compare Flemish wafer, altered from Middle Dutch wafel "honeycomb;" see waffle (n.)). Eucharistic bread first so called 1550s.
waffle (n.): "kind of batter-cake, baked crisp in irons and served hot," 1744, from Dutch wafel "waffle," from Middle Dutch or Middle Low German wafel, from Proto-Germanic *wabila- "web, honeycomb" (source also of Old High German waba "honeycomb," German Wabe), related to Old High German weban, Old English wefan "to weave" (see weave (v.)). Sense of "honeycomb" is preserved in some combinations referring to a weave of cloth. Waffle iron is from 1794.
waffle (v.): 1690s, "to yelp, bark," frequentative of provincial waff "to yelp, to bark like a puppy" (1610); possibly of imitative origin. Figurative sense of "talk foolishly" (c. 1700) led to that of "vacillate, equivocate" (1803), originally a Scottish and northern English usage. Late 17c. Scottish also had waff "act of waving," variant of waft, which might have influenced the sense. Related: Waffled; waffler; waffling.
waft (v.): c. 1500, transitive, "to move gently" (through the air), probably from Middle Dutch or Middle Low German, ultimately from wachten "to guard" (perhaps via notion of a ship that guards another as it sails), related to waken "rouse from sleep," from Proto-Germanic *waht- (see wake (n.1)). Possibly influenced by northern dialect waff "cause to move to and fro" (1510s), a variant of wave. Intransitive sense from 1560s. Related: Wafted; wafting.
wag (v.): early 13c. (intransitive), "waver, vacillate, lack steadfastness," probably from a Scandinavian source (compare Old Norse vagga "a cradle," Danish vugge "rock a cradle," Old Swedish wagga "fluctuate, rock" a cradle), and in part from Old English wagian "move backwards and forwards;" all from Proto-Germanic *wag- (source also of Old High German weggen, Gothic wagjan "to wag"), probably from PIE root *wegh- "to move about" (see weigh).

Transitive meaning "move (something) back and forth or up and down" is from c. 1300; of dogs and their tails from mid-15c.: "and whanne they [hounds] see the hure maystre they wol make him cheere and wagge hur tayles upon him." [Edward, Duke of York, "The Master of Game," 1456]. Related: Wagged; wagging. Wag-at-the-wall (1825) was an old name for a hanging clock with pendulum and weights exposed.
wag (n.1): "person fond of making jokes," 1550s, perhaps a shortening of waghalter "gallows bird," person destined to swing in a noose or halter, applied humorously to mischievous children, from wag (v.) + halter. Or possibly directly from wag (v.); compare wagger "one who stirs up or agitates" (late 14c.).
wag (n.2): "act of wagging," 1580s, from wag (v.).
wage (n.): c. 1300, "a payment for services rendered, reward, just deserts;" mid-14c., "salary paid to a provider of service," from Anglo-French and Old North French wage (Old French gage) "pledge, pay, reward," from Frankish *wadja- or another Germanic source (compare Old English wedd "pledge, agreement, covenant," Gothic wadi "pledge"), from Proto-Germanic *wadi- (see wed (v.)).

Also from mid-14c., "a pledge, guarantee, surety" (usually in plural), and (c. 1400) "a promise or pledge to meet in battle." The "payment for service" sense by late 14c. extended to allotments of money paid at regular intervals for continuous or repeated service. Traditionally in English wages were payment for manual or mechanical labor and somewhat distinguished from salary or fee. Modern French cognate gages (plural) means "wages of a domestic," one of a range of French "pay" words distinguished by class, such as traitement (university professor), paye, salaire (workman), solde (soldier), récompense, prix. The Old English word was lean, related to loan and representing the usual Germanic word (Gothic laun, Dutch loon, German lohn). Wage-earner attested from 1871.
wage (v.): c. 1300, "give (something) as surety, deposit as a pledge," from Old North French wagier "to pledge" (Old French gagier, "to pledge, guarantee, promise; bet, wager, pay," Modern French gager), from wage (see wage (n.)). Meaning "to carry on, engage in" (of war, etc.) is attested from mid-15c., probably from earlier sense of "to offer as a gage of battle, agree to engage in combat" (mid-14c.). Related: Waged; waging.
wager (n.): c. 1300, wajour "a promise, a vow, something pledged or sworn to;" also "a bet, a wager; stakes, something laid down as a bet," from Anglo-French wageure, Old North French wagiere (Old French gagiere, Modern French gageure) "pledge, security," from wagier "to pledge" (see wage (n.)).
wager (v.): c. 1600 (intransitive); 1610s (transitive), from wager (n.). Related: Wagered; wagering.
waggish (adj.): "willing to make a fool of oneself, and fond of doing so to others," 1580s, from wag (n.) + -ish. Related: Waggishly; waggishness.
waggle (v.): late 15c. (implied in waggling), frequentative of wag (v.). Compare Dutch waggelen "to waggle," Old High German wagon "to move, shake," German wackeln "to totter." Transitive sense from 1590s. Related: Waggled.
wagon (n.): "four-wheeled vehicle to carry heavy loads," late 15c., from Middle Dutch wagen, waghen, from Proto-Germanic *wagnaz (source also of Old English wægn, Modern English wain, Old Saxon and Old High German wagan, Old Norse vagn, Old Frisian wein, German Wagen), from PIE *wogh-no-, suffixed form of root *wegh- "to carry, to move" (source also of Sanskrit vahanam "vessel, ship," Greek okhos, Latin vehiculum, Old Church Slavonic vozŭ "carriage, chariot," Russian povozka, Lithuanian va žis "a small sledge," Old Irish fen, Welsh gwain "carriage, cart;" see weigh).

In Dutch and German, the general word for "a wheel vehicle;" English use is a result of contact through Flemish immigration, Dutch trade, or the Continental wars. It has largely displaced the native cognate, wain. Spelling preference varied randomly between -g- and -gg- from mid-18c., before American English settled on the etymological wagon, while waggon remained common in Great Britain. Wagon-train is attested from 1810. Phrase on the wagon "abstaining from alcohol" is 1904, originally on the water cart.
wagtail (n.): c. 1500, kind of small bird that has its tail in continuous motion (late 12c. as a surname), earlier wagstart (mid-15c.), from wag (v.) + tail (n.). From 18c. as "a harlot," but this sense seems to be implied much earlier:
If therefore thou make not thy mistress a goldfinch, thou mayst chance to find her a wagtaile. [Lyly, "Midas," 1592]
wah-wah: 1926, in jazz slang, in reference to the effect on brass instruments made by manipulating the mute; of imitative origin. Later also in reference to an electric guitar effect. As an imitation of the sound of a baby crying, it is recorded from 1938. Wah-wah pedal is recorded from 1969. Compare Chinook jargon wawa "talk, speak, call, ask, sermon, language;" Cree (Algonquian) wehwew "goose," Lenape (Algonquian) wava "snow goose," all probably of imitative origin.
Wahabi (n.): 1807, follower of Islamic fundamentalist Abd-el-Wahhab (1691-1787), from his name, with Arabic genitive suffix -i. Related: Wahabiism; Wahabism.
wahoo (n.): type of large marine fish caught near Key West, 1884, of unknown origin. As the name of North American trees or shrubs, 1770, from distortions of native names; especially the "burning bush," from Dakota (Siouan) wahu, from wa- "arrow" + -hu "wood." In reference to the winged elm, it is from Muskogee vhahwv.
waif (n.): late 14c., "unclaimed property, flotsam, stray animal," from Anglo-French waif (13c., Old French guaif) "ownerless property, something lost;" as an adjective, "not claimed, outcast, abandoned," probably from a Scandinavian source akin to Old Norse veif "waving thing, flag," from Proto-Germanic *waif-, from PIE *weip- "to turn, vacillate, tremble ecstatically" (see vibrate). Compare Medieval Latin waivium "thing thrown away by a thief in flight." A Scottish/northern English parallel form was wavenger (late 15c.).

Meaning "person (especially a child) without home or friends" first attested 1784, from legal phrase waif and stray (1620s), from the adjective in the sense "lost, strayed, homeless." Neglected children being uncommonly thin, the word tended toward this sense. Connotations of "fashionable, small, slender woman" began 1991 with application to childishly slim supermodels such as Kate Moss.
waifish (adj.): 1870, from waif + -ish. Related: Waifishly; waifishness.
wail (v.): c. 1300 (intransitive); mid-14c. (transitive), from Old Norse væla "to lament," from væ "woe" (see woe). Of jazz musicians, "to play very well," attested from 1955, American English slang (wailing "excellent" is attested from 1954). Related: Wailed; wailer.
wail (n.): c. 1300; see wail (v.).
wain (n.): Old English wægn "wheeled vehicle, wagon, cart," from Proto-Germanic *wagnaz (see wagon). Largely fallen from use by c. 1600, but kept alive by poets, who found it easier to rhyme on than wagon. As a name for the Big Dipper/Plough, it is from Old English (see Charles's Wain).
wainscot (n.): mid-14c., "imported oak of superior quality" (well-grained and without knots), probably from Middle Dutch or Middle Flemish waghenscote "superior quality oak wood, board used for paneling" (though neither of these is attested as early as the English word), related to Middle Low German wagenschot (late 14c.), from waghen (see wagon) + scote "partition, crossbar." So called perhaps because the wood originally was used for wagon building and coachwork, but the sense evolution is not entirely clear. Meaning "panels lining the walls of rooms" is recorded from 1540s. Wainscoting is from 1570s.
wainwright (n.): "wagon-builder," Old English wægn-wyrhta; see wain + wright.
waist (n.): late 14c., "middle part of the body," also "part of a garment fitted for the waist, portion of a garment that covers the waist" (but, due to fashion styles, often above or below it), probably from Old English *wæst "growth," hence, "where the body grows," from Proto-Germanic *wahs-tu- (source also of Old English wæstm, Old Norse vöxtr, Swedish växt, Old High German wahst "growth, increase," Gothic wahstus "stature," Old English weaxan "to grow" see wax (v.)), from PIE *wegs-, extended form of root *aug- (1) "to increase" (see augment).
waistband (n.): 1580s, from waist + band (n.1).
waistcoat (n.): 1510s, from waist + coat (n.).
waisted (adj.): c. 1400, "fitted with a (specified type of) waist," from waist.
waistline (n.): also waist-line, 1867, from waist + line (n.).
wait (v.): c. 1200, "to watch with hostile intent, lie in wait for, plot against," from Anglo-French and Old North French waitier "to watch" (Old French gaitier "defend, watch out, be on one's guard; lie in wait for;" Modern French guetter), from Frankish *wahton or another Germanic source, from Proto-Germanic *waht- (source also of Dutch wacht "a watching," Old High German wahten, German wachten "to watch, to guard;" Old High German wahhon "to watch, be awake," Old English wacian "to be awake;" see wake (v.)). General sense of "remain in some place" is from late 14c.; that of "to see to it that something occurs" is late 14c. Meaning "to stand by in attendance on" is late 14c.; specific sense of "serve as an attendant at a table" is from 1560s. Related: Waited; waiting.

To wait (something) out "endure a period of waiting" is recorded from 1849. Waiting room is attested from 1680s. Waiting list is recorded from 1841; the verb wait-list "to put (someone) on a waiting list" is recorded from 1960. Waiting game is recorded from 1835, originally in horse-racing.
When speed, not stoutness, is the best of a horse, quite a contrary system is practised. With such a horse, the jockey plays a waiting game; that is, he carefully nurses him through the race, so as not to distress him by overpacing him; as the finish approaches, he creeps up to his horses by degrees, but does not quit them to go in front till he sees that the pace has made them "safe," -- when he lets loose and wins. [James Christie Whyte, "History of the British Turf," London, 1840]
wait (n.): early 13c., "a watcher, onlooker," from Old North French wait (Old French gait "look-out, watch, sentry"), from Old North French waitier (Old French gaitier; see wait (v.)). Compare Old High German wahta, German Wacht "a watchman." From late 14c. as "an ambush, a trap" (as in lie in wait). From 1855 as "time occupied in waiting;" 1873 as "an act of waiting." From the sense "civic employee responsible for signaling the hour or an alarm by sounding on a trumpet, etc." comes the old sense "town musicians" (mid-15c.).
waiter (n.): late 14c., "attendant, watchman," agent noun from wait (v.). Sense of "attendant at a meal, servant who waits at tables" is from late 15c., originally in reference to household servants; in reference to inns, eating houses, etc., it is attested from 1660s.
waitress (n.): "woman who waits tables at a restaurant," 1834, from waiter + -ess.
waitstaff (n.): 1981, American English; see waiter + staff (n.).