Yiddish (n.) Look up Yiddish at Dictionary.com
1875, from Yiddish yidish, from Middle High German jüdisch "Jewish" (in phrase jüdisch deutsch "Jewish-German"), from jude "Jew," from Old High German judo, from Latin Judaeus (see Jew). The English word has been re-borrowed in German as jiddisch. As an adjective from 1886. Related: Yiddishism.
yield (v.) Look up yield at Dictionary.com
Old English gieldan (West Saxon), geldan (Anglian) "to pay, pay for; reward, render; worship, serve, sacrifice to" (class III strong verb; past tense geald, past participle golden), from Proto-Germanic *geldan "pay" (cognates: Old Saxon geldan "to be worth," Old Norse gjaldo "to repay, return," Middle Dutch ghelden, Dutch gelden "to cost, be worth, concern," Old High German geltan, German gelten "to be worth," Gothic fra-gildan "to repay, requite"). This is from PIE *gheldh- "to pay," a root found only in Balto-Slavic and Germanic (and Old Church Slavonic žledo, Lithuanian geliuoti might be Germanic loan-words).

"[T]he only generally surviving senses on the Continent are 'to be worth; to be valid, to concern, apply to,' which are not represented at all in the English word" [OED]; sense development in English comes via use of this word to translate Latin reddere, French rendre. Sense of "give in return for labor or capital invested" is from early 14c. Intransitive sense of "give oneself up, submit, surrender (to a foe)" is from c.1300. Related to Middle Low German and Middle Dutch gelt, Dutch geld, German Geld "money." Related: Yielded; yielding.
yield (n.) Look up yield at Dictionary.com
Old English gield "payment, sum of money; service, offering, worship;" from the source of yield (v.). Extended sense of "production" (as of crops) is first attested mid-15c. Earliest English sense survives in financial "yield from investments."
yielding (adj.) Look up yielding at Dictionary.com
late 14c., "generous in rewarding," present participle adjective from yield (v.). From 1660s as "giving way to physical force."
yikes Look up yikes at Dictionary.com
exclamation of alarm or surprise, by 1953; perhaps from yoicks, a call in fox-hunting, attested from c.1770. Yike "a fight" is slang attested from 1940, of uncertain connection.
yin (n.) Look up yin at Dictionary.com
feminine or negative principle in Chinese philosophy, 1670s, from Chinese (Mandarin) yin, said to mean "female, night, lunar," or "shade, feminine, the moon." Compare yang. Yin-yang is from 1850.
yins (pron.) Look up yins at Dictionary.com
"you people, you-all," contracted from U.S. dialectal you-uns, for you-ones (see you, also see y'all); first noted 1810 in Ohio. Also yinz; now considered a localism in Pittsburgh, Pa.
yip (v.) Look up yip at Dictionary.com
1891, possibly from dialectal yip "to cheep like a bird" (early 19c.), from Middle English yippen (mid-15c.), of imitative origin. As a noun from 1896.
yippee (interj.) Look up yippee at Dictionary.com
interjection of pleasure, exultation, etc., 1920; perhaps an extension and modification of hip (interj.).
Yippie Look up Yippie at Dictionary.com
1968, acronym from fictitious "Youth International Party," modeled on hippie.
On December 31, 1967, Abbie [Hoffman], Jerry [Rubin], Paul Krassner, Dick Gregory, and friends decided to pronounce themselves the Yippies. (The name came first, then the acronym that would satisfy literal-minded reporters: Youth International Party.) [Todd Gitlin," The Sixties," 1987, p.235]
YMCA (n.) Look up YMCA at Dictionary.com
also Y.M.C.A., 1868, initialism (acronym) of Young Men's Christian Association.
yo Look up yo at Dictionary.com
as a greeting, 1859, but the word is attested as a sailor's or huntsman's utterance since early 15c. Modern popularity dates from World War II (when, it is said, it was a common response at roll calls) and seems to have been most intense in Philadelphia.
yo-yo (n.) Look up yo-yo at Dictionary.com
1915, apparently from a language of the Philippines. Registered as a trademark in Vancouver, Canada, in 1932, the year the first craze for them began (subsequent fads 1950s, 1970s, 1998). The toy itself is much older and was earlier known as bandalore (1802), a word of obscure origin, "but it was from American contact in the Philippines that the first commercial development was established" [Century Dictionary]. Figurative sense of any "up-and-down movement" is first recorded 1932. Meaning "stupid person" is recorded from 1970. The verb in the figurative sense is attested from 1967.
yob (n.) Look up yob at Dictionary.com
"a youth," 1859, British English, back-slang from boy. By 1930s with overtones of "hooligan, lout." Related: extended form yobbo.
yod (n.) Look up yod at Dictionary.com
10th and smallest letter of the Hebrew alphabet (compare jot, iota).
yodel (v.) Look up yodel at Dictionary.com
"sing by sudden changing to and from falsetto," 1827, from German jodeln, from dialectal German jo, an exclamation of joy, of imitative origin. As a noun from 1849.
yoga (n.) Look up yoga at Dictionary.com
1820, from Hindi yoga, from Sanskrit yoga-s, literally "union, yoking" (with the Supreme Spirit), from PIE root *yeug- "to join" (see jugular). Related: Yogic.
yogh (n.) Look up yogh at Dictionary.com
Middle English letter (Ȝ), c.1300; see Y. The name probably is identical with yoke (Middle English yogh) and so called because yoke began with a yogh.
yogi (n.) Look up yogi at Dictionary.com
"one who practices yoga," 1610s, from Hindi yogi, from Sanskrit yoga- (see yoga). Related: Yogism.
yogurt (n.) Look up yogurt at Dictionary.com
also yoghurt, 1620s, a mispronunciation of Turkish yogurt, in which the -g- is a "soft" sound, in many dialects closer to an English "w." The root yog means roughly "to condense" and is related to yogun "intense," yogush "liquify" (of water vapor), yogur "knead."
yok (n.) Look up yok at Dictionary.com
slang, "gentile, non-Jew," pejorative, 1920, from Yiddish, where it is back slang, a reversed and altered form of goy.
yoke (n.) Look up yoke at Dictionary.com
Old English geoc "contrivance for fastening a pair of draft animals," earlier geoht "pair of draft animals" (especially oxen), from Proto-Germanic *yukam (cognates: Old Saxon juk, Old Norse ok, Danish aag, Middle Dutch joc, Dutch juk, Old High German joh, German joch, Gothic juk "yoke"), from PIE root *yeug- "to join" (see jugular). Figurative sense of "heavy burden, oppression, servitude" was in Old English.
yoke (v.) Look up yoke at Dictionary.com
Old English geocian "to yoke, join together," from yoke (n.). Related: Yoked; yoking.
yokel (n.) Look up yokel at Dictionary.com
1812, perhaps from dialectal German Jokel, disparaging name for a farmer, originally diminutive of Jakob. Or perhaps from English yokel, dialectal name for "woodpecker."
yolk (n.) Look up yolk at Dictionary.com
Old English geolca, geoloca "yolk," literally "the yellow part," from geolu "yellow" (see yellow (adj.)). Formerly also spelled yelk.
Yom Kippur Look up Yom Kippur at Dictionary.com
Jewish holiday, 1854, from Mishnaic Hebrew yom kippur (in Biblical Hebrew, yom kippurim), literally "day of atonement," from yom "day" + kippur "atonement, expiation."
yon (adj., pron.) Look up yon at Dictionary.com
Old English geon "that (over there)," from Proto-Germanic *jaino- (cognates: Old Frisian jen, Old Norse enn, Old High German ener, Middle Dutch ghens, German jener, Gothic jains "that, you"), from PIE pronomial stem *i- (cognates: Sanskrit ena-, third person pronoun, anena "that;" Latin idem "the same," id "it, that one;" Old Church Slavonic onu "he;" Lithuanian ans "he"). As an adverb from late 15c., a shortening of yonder.
yond (adv., prep.) Look up yond at Dictionary.com
Old English geond "beyond, yonder," related to geon (see yon).
yonder (adv.) Look up yonder at Dictionary.com
"within sight but not near," c.1300, from Old English geond "throughout, up to, as far as" (see yond) + comparative suffix -er (2). Cognate with Middle Low German ginder, Middle Dutch gender, Dutch ginder, Gothic jaindre. Now replaced except in poetic usage by ungrammatical that.
yoni (n.) Look up yoni at Dictionary.com
1799, from Sanskrit, "female sexual principle as an object of veneration," literally "vulva, womb."
yoo-hoo (interj.) Look up yoo-hoo at Dictionary.com
exclamation to call attention, by 1913.
yore (adv.) Look up yore at Dictionary.com
Old English geara "of yore, formerly, in former times," literally "of years," originally adverbial genitive plural of gear (see year), and used without of. As a noun from mid-14c.
York Look up York at Dictionary.com
city in northern England, Old English Eoforwic, earlier Eborakon (c.150), an ancient Celtic name, probably meaning "Yew-Tree Estate," but Eburos may also be a personal name. Related: Yorkist; Yorkish; Yorker. Yorkshire pudding is recorded from 1747; Yorkshire terrier first attested 1872; short form Yorkie is from 1950.
Yoruba Look up Yoruba at Dictionary.com
west Nigerian people, also the name of their language.
Yosemite Look up Yosemite at Dictionary.com
from Southern Sierra Miwok /yohhe'meti/ "they are killers." "[E]vidently a name given to the Indians of the valley by those outside it." [Bright]
you (pron.) Look up you at Dictionary.com
Old English eow, dative and accusative plural of þu (see thou), objective case of ge, "ye" (see ye), from Proto-Germanic *juz-, *iwwiz (cognates: Old Norse yor, Old Saxon iu, Old Frisian iuwe, Middle Dutch, Dutch u, Old High German iu, iuwih, German euch), from PIE *yu, second person (plural) pronoun.

Pronunciation of you and the nominative form ye gradually merged from 14c.; the distinction between them passed out of general usage by 1600. Widespread use of French in England after 12c. gave English you the same association as French vous, and it began to drive out singular nominative thou, originally as a sign of respect (similar to the "royal we") when addressing superiors, then equals and strangers, and ultimately (by c.1575) becoming the general form of address. Through 13c. English also retained a dual pronoun ink "you two; your two selves; each other."
young (n.) Look up young at Dictionary.com
"young animals collectively, offspring," late 15c., from young (adj.).
young (adj.) Look up young at Dictionary.com
Old English geong "youthful, young; recent, new, fresh," from Proto-Germanic *juwunga- (cognates: Old Saxon and Old Frisian jung, Old Norse ungr, Middle Dutch jonc, Dutch jong, Old High German and German jung, Gothic juggs), from PIE *yuwn-ko-, suffixed form of root *yeu- "vital force, youthful vigor" (cognates: Sanskrit yuva "young," Latin juvenis "young," Lithuanian jaunas, Old Church Slavonic junu, Russian junyj "young," Old Irish oac, Welsh ieuanc "young").

From c.1830-1850, Young France, Young Italy, etc., were loosely applied to "republican agitators" in various monarchies; also, especially in Young England, Young America, used generally for "typical young person of the nation." For Young Turk, see Turk.
youngster (n.) Look up youngster at Dictionary.com
1580s, from young + -ster. Earlier was youngling, from Old English geongling.
younker Look up younker at Dictionary.com
c.1500, "young nobleman," from Middle Dutch jonckher (Dutch jonker), from jonc "young" (see young (adj.)) + here "lord, master" (see Herr). Compare junker.
your Look up your at Dictionary.com
Old English eower, possessive pronomial adjective, genitive of ge "ye" (see ye), from Proto-Germanic base of you. Cognate with Old Saxon iuwar, Old Frisian iuwer, Old Norse yðvarr, Old High German iuwer, German euer, Gothic izwar "your." Used in titles of honor by mid-14c.
yourn (pron.) Look up yourn at Dictionary.com
dialectal possessive pronoun from your, attested from late 14c. See her.
yours (pron.) Look up yours at Dictionary.com
absolutive form of your, c.1300, on model of his, ours, etc. Yours truly "myself" is from 1833, from the common subscription of letters.
It is difficult to say what will succeed, and still more to pronounce what will not. I am at this moment in that uncertainty (on our own score,) and it is no small proof of the author's powers to be able to charm and fix a mind's attention on similar subjects and climates in such a predicament. That he may have the same effect upon all his readers is very sincerely the wish, and hardly the doubt, of yours truly,
[Lord Byron to John Murray, Dec. 4, 1813]
yourself Look up yourself at Dictionary.com
by early 14c., from your + self. Plural yourselves first recorded 1520s.
youse Look up youse at Dictionary.com
dialectal inflection of you, 1876, not always used in plural senses.
youth (n.) Look up youth at Dictionary.com
Old English geoguð "youth; young people, junior warriors; young of cattle," related to geong "young," from Proto-Germanic *jugunthi- (cognates: Old Saxon juguth, Old Frisian jogethe, Middle Dutch joghet, Dutch jeugd, Old High German jugund, German Jugend, Gothic junda "youth"), from suffixed form of PIE root *yeu- "vital force, youthful vigor" (see young (adj.)) + Proto-Germanic abstract noun suffix *-itho (see -th (2)).

According to OED, the Proto-Germanic form apparently was altered from *juwunthiz by influence of its contrast, *dugunthiz "ability" (source of Old English duguð). In Middle English, the medial -g- became a yogh, which then disappeared.
They said that age was truth, and that the young
Marred with wild hopes the peace of slavery
youthful (adj.) Look up youthful at Dictionary.com
1560s, from youth + -ful. Old English had geoguðlic. Other words formerly used in the same sense were youthlike, youthly, youthsome, youthy. Related: Youthfulness.
yow Look up yow at Dictionary.com
exclamation, with various meanings, mid-15c.
yowl (v.) Look up yowl at Dictionary.com
c.1200, yuhelen, probably of imitative origin. Related: Yowled; yowling. The noun is recorded from mid-15c.
yowza Look up yowza at Dictionary.com
colloquial form of yes, sir, 1934, popularized by U.S. bandleader and radio personality Ben "The Old Maestro" Bernie (1891-1943).