Online Etymology Dictionary

yogurt (n.): 1620s, a mispronunciation of Turk. 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.): slang, "gentile, non-Jew," pejorative, 1920, from Yiddish, a reversed and altered form of goy.
yoke (n.): Old English geoc "yoke," earlier geoht "pair of draft animals," from Proto-Germanic *yukam (cf. Old Saxon juk, Old Norse ok, Danish aag, Middle Dutch joc, Dutch juk, Old High German joh, German joch, Gothic juk "yoke"), from PIE *jugom "joining" (see jugular). Figurative sense of "heavy burden, oppression, servitude" was in Old English.
yoke (v.): Old English geocian, from yoke (n.). Related: Yoked; yoking.
yokel (n.): 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: Old English geolca, geoloca "yolk," literally "the yellow part," from geolu "yellow" (see yellow). Formerly also spelled yelk.
Yom Kippur: Jewish holiday, 1854, from Mishnaic Hebrew yom kippur (in Biblical Hebrew, yom kippurim), literally "day of atonement," from yom "day" + kippur "atonement, expiation."
yon: Old English geon (adj.) "that (over there)," from Proto-Germanic *jaino- (cf. Old Frisian jen, Old Norse enn, Old High German ener, Middle Dutch ghens, German jener, Gothic jains "that, you"), from PIE pronomial stem *i- (cf. Sanskrit ena-, third person pronoun, anena "that;" Latin idem "the same," id "it, that one;" Old Church Slavonic onu "he;" Lithuanian ans "he").
yond: Old English geond (adv., prep.) "beyond, yonder," related to geon (see yon).
yonder: c.1300, from Old English geond (see yond) + comp. suffix -er (2). Now replaced except in poetic usage by ungrammatical that.
yoni (n.): 1799, from Sanskrit, "female sexual principle as an object of veneration," literally "vulva, womb."
yoo-hoo: exclamation to call attention, 1924.
yore: Old English geara (adv.) "of yore," originally genitive plural of gear (see year), and used without of.
York: 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. Yorkshire pudding is recorded from 1747; Yorkshire terrier first attested 1872; short form Yorkie is from 1950.
Yosemite: 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: Old English eow, dative and accusative plural of þu (see thou), objective case of ge, "ye" (see ye), from West Germanic *iuwiz (cf. Old Norse yor, Old Saxon iu, Old Frisian iuwe, Middle Dutch, Dutch u, Old High German iu, iuwih, German euch), from PIE *ju.

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. For a more thorough discussion of this, go here. Through 13c. English also retained a dual pronoun ink "you two; your two selves; each other."

Words for "you" in Japanese include anata (formal, used by a wife when addressing her husband), kimi (intimate, used among friends) or the rougher omae (oh-MAI-aye), used when talking down to someone or among male friend showing their manliness. Dial. you-uns, for you-ones, first noted 1810 in Ohio.
young (n.): "young animals collectively, offspring," late 15c., from young (adj.).
young (adj.): Old English geong "youthful, young," from Proto-Germanic *jungas (cf. Old Saxon and Old Frisian jung, Old Norse ungr, Middle Dutch jonc, Dutch jong, Old High German and German jung, Gothic juggs), from PIE *juwngkos, from PIE root *yeu- "vital force, youthful vigor" (cf. 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.): 1580s, from young + -ster. Earlier was youngling, from Old English geongling.
younker: c.1500, “young nobleman,” from Middle Dutch jonckher (Dutch jonker), from jonc “young” + here “lord, master.” Cf. junker.
your: Old English eower, genitive of ge "ye" (see ye), from Proto-Germanic base of you. Cf. 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. Absolutive form yours is attested from c.1300. For dialectal yourn, see her. Yours truly "myself" is from 1833, from the common subscription of letters.
yourn: dialectal possessive pronoun from your, attested from late 14c. See her.
yourself: by early 14c., from your + self. Plural yourselves first recorded 1520s.
youse: dialectal inflection of you, 1893, not always used in plural senses.
youth (n.): Old English geoguð "youth," related to geong "young," from West Germanic *jugunthiz, altered from Proto-Germanic *juwunthiz (cf. Old Saxon juguth, Old Frisian jogethe, Middle Dutch joghet, Dutch jeugd, Old High German jugund, German Jugend, Gothic junda "youth;" see young) 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
[Shelley]
youthful (adj.): 1560s, from youth + -ful. Related: Youthfulness.
yow: exclamation, with various meanings, mid-15c.
yowl (v.): early 13c., yuhelen, probably of imitative origin. The noun is recorded from mid-15c. Related: Yowled; yowling.
yowza: colloquial form of yes, sir, 1934, popularized by U.S. bandleader and radio personality Ben "The Old Maestro" Bernie (1891-1943).
ytterbium: metallic rare-earth element, 1879, coined in Modern Latin by Swedish chemist Carl Gustaf Mosander (1797-1858) from Ytterby, name of a town in Sweden where mineral containing it was found.
yttrium: metallic rare-earth element, 1866, coined in Modern Latin by Swedish chemist Carl Gustaf Mosander (1797-1858) from Ytterby, name of a town in Sweden where mineral containing it was found.
yuan: Chinese unit of currency introduced 1914, from Chinese yuan "round, round object, circle."
Yucatan: said to be from a local word meaning “massacre.”
yucca (n.): Central and South American name for the cassava plant, 1550s, from Spanish yuca, juca (late 15c.), probably from Taino, native language of Haiti.
yuck (1): exclamation of disgust, 1966, origin perhaps echoic (cf. Newfoundland slang yuck "to vomit," 1963).
yuck (2): "laugh," 1938, yock, probably imitative.
yucky (adj.): 1970, from yuck (1) + -y (2). Related: Yuckiness.
Yugoslav: 1853, from Slav (q.v.) + Serbo-Cr. jugo- "south,"comb. form of jug "south, south wind, noon," from Old Church Slavonic jugu.
Yugoslavia: 1929 (earlier the country was Kingdom of the Serbs, Croats, and Slovenes); from Yugoslav + -ia. The name vanished from the map in 2003.
yuk: “laughter, something evoking laughs,” 1964, imitative; see yuck (2).
yule (n.): Old English geol, geola "Christmas Day, Christmastide," from Old Norse jol (plural), a heathen feast, later taken over by Christianity, of unknown origin.

The Old English (Anglian) cognate giuli was the Anglo-Saxons' name for a two-month midwinter season corresponding to Roman December and January, a time of important feasts but not itself a festival. After conversion to Christianity it narrowed to mean "the 12-day feast of the Nativity" (which began Dec. 25), but was replaced by Christmas by 11c., except in the northeast (areas of Danish settlement), where it remained the usual word.

Revived 19c. by writers to mean "the Christmas of 'Merrie England.' " First direct reference to the Yule log is 17c. Old Norse jol seems to have been borrowed in Old French as jolif, hence Modern French joli "pretty, nice," originally "festive" (see jolly).
yuletide (n.): late 15c., from yule + tide.
yum: exclamation of pleasure, attested from 1878.
yummy: "delicious," 1899, from baby talk. Yum-yum as an exclamation of pleasure is recorded from 1878.
yup: 1906, variant of yes.
yuppie: 1982, acronym from "young urban professional," ousting competition from yumpie (1984), from "young upward-mobile professional," and yap (1984), from "young aspiring professional." The word was felt as an insult by 1985.
yurt: 1784, ultimately from Russian yurta, from a Turkic language and originally meaning “home, dwelling.”