Online Etymology Dictionary

Weimar (adj.): in reference to the pre-1933 democratic government of Germany, 1932, from name of city in Thuringia where German constitution was drawn up in 1919. The place name is a compound of Old High German wih "holy" + mari "lake."
Weimaraner (n.): dog breed, 1943, from Weimar, german city, + German suffix -aner indicating "of this place." Originally bred as a hunting dog in the Weimar region.
weir (n.): Old English wer "dam, fence, enclosure," especially one for catching fish (related to werian "dam up"), from Proto-Germanic *warjanan (cf. Old Norse ver, Old Frisian and Middle Dutch were, Dutch weer, Old High German wari, German Wehr "defense, protection," Gothic warjan "to defend, protect"), from PIE *wer- "to cover, shut" (cf. Sanskrit vatah "enclosure," vrnoti "covers, wraps, shuts;" Lithuanian uzveriu "to shut, to close;" Old Persian *pari-varaka "protective;" Latin (op)erire "to cover;" Old Church Slavonic vora "sealed, closed," vreti "shut;" Old Irish feronn "field," properly "enclosed land").
weird: Old English wyrd (n.) "fate, destiny," literally "that which comes," from Proto-Germanic *wurthis (cf. Old Saxon wurd, Old High German wurt "fate," Old Norse urðr "fate, one of the three Norns"), from PIE *wert- "to turn, wind," (cf. German werden, Old English weorðan "to become"), from root *wer- (3) "to turn, bend" (see versus). For sense development from "turning" to "becoming," cf. phrase turn into "become."

The modern sense of weird developed from Middle English use of weird sisters for the three fates or Norns (in Germanic mythology), the goddesses who controlled human destiny. They were portrayed as odd or frightening in appearance, as in "Macbeth," which led to the adjectival meaning "odd-looking, uncanny," first recorded 1815.
weirdo (n.): "strange person," 1955, from weird. Cf. earlier Scot. weirdie (1894).
welch (v.): 1857, racing slang, "to refuse or avoid payment of money laid as a bet," probably a disparaging use of the national name Welsh. Related: Welched; welching.
welcome (n.): Old English wilcuma, exclamation of kindly greeting, from earlier wilcuma (n.) "welcome guest," literally "one whose coming is in accord with another's will," from willa "pleasure, desire, choice" (see will (v.)) + cuma "guest," related to cuman (see come). Cf. Old High German willicomo, Middle Dutch wellecome. Meaning "entertainment or public reception as a greeting" is recorded from 1530. You're welcome as a formulaic response to thank you is attested from 1907. Welcome mat first recorded 1951; welcome wagon is attested from 1961.
welcome (v.): Old English wilcumian, from wilcuma (see welcome (n.)). Related: Welcomed; welcoming.
weld (n.2): "joint formed by welding," 1831, from weld (v.).
weld (v.): 1590s, alteration of well (v.) "to boil, rise;" influenced by past participle form welled. Related: Welded; welding.
weld (n.1): plant (Resedo luteola) producing yellow dye, late 14c., from Old English *wealde, perhaps a variant of Old English wald "forest" (cf. Middle Low German walde, Middle Dutch woude). Spanish gualda, French gaude are Germanic loan-words.
welfare (n.): Old English wel faran "condition of being or doing well," from wel (see well (adv.)) + faran "get along" (see fare (v.)). Cf. Old Norse velferð. Meaning "social concern for the well-being of children, the unemployed, etc." is first attested 1904. Welfare state is recorded from 1941.
welkin (n.): "sky" (poetic), Old English wolcen "cloud," from Proto-Germanic *welk- (cf. Old Saxon wolkan, Old Frisian wolken, Middle Dutch wolke, Dutch wolk, Old High German wolka, German Wolke "cloud," from PIE *welgh- "wet" (cf. Lithuanian vilgyti "to moisten," Old Church Slavonic viaga "moisture," Czech vlhky "damp").
well (adv.): "in a satisfactory manner," Old English wel, common Germanic (cf. Old Saxon wela, Old Norse vel, Old Frisian wel, Dutch wel, Old High German wela, German wohl, Gothic waila "well"), from PIE *wel-, *wol- (cf. Sanskrit prati varam "at will," Old Church Slavonic vole "well," Welsh gwell "better," Latin velle "to wish, will," Old English willan "to wish;" see will (v.)). Also used in Old English as an interjection and an expression of surprise. Well-to-do "prosperous" is recorded from 1825.
well (v.): "to spring, rise, gush," Old English wiellan (Anglian wællan), causative of weallan "to boil, bubble up" (class VII strong verb; past tense weoll, past participle weallen), from Proto-Germanic *wal-, *wel- "roll" (cf. Old Saxon wallan, Old Norse vella, Old Frisian walla, Old High German wallan, German wallen, Gothic wulan "to bubble, boil"), from PIE root *wel- "to turn, roll" (see vulva), on notion of "roiling or bubbling water."
well (n.): "hole dug for water, spring of water," Old English wielle (West Saxon), welle (Anglian), from wiellan (see well (v.)).
well-adjusted (adj.): 1735, in reference to mechanisms, etc., from well (adv.) + past participle of adjust. In reference to emotional balance, recorded from 1959.
well-behaved (adj.): 1590s, from well (adv.) + past participle of behave.
well-being (n.): 1610s, from well (adv.) + gerundive of be.
well-beloved (adj.): late 14c., from well (adv.) + beloved.
well-done (adj.): c.1200, "wise, prudent," from well (adv.) + past participle of do. Meaning "thoroughly cooked," in reference to meat, is attested from 1747. Well done! as an exclamation of approval is recorded from mid-15c.
well-earned (adj.): 1730, from well (adv.) + past participle of earn.
well-endowed (adj.): 1680s, "with ample material endowments," from well (adv.) + past participle of endow. Sexual sense is attested from 1951.
well-heeled (adj.): 1897, from well (adv.) + colloquial sense of heeled (see heel (n.)).
well-hung (adj.): 1610s, in male genital sense, from well (adv.) + past participle of hang.
well-intentioned (adj.): 1590s, from well (adv.) + intentioned (see intention).
well-kept (adj.): c.1400, from well (adv.) + past participle of keep.
well-known (adj.): late 15c., from well (adv.) + past participle of know.
well-nigh (adv.): Old English wel neah, from well (adv.) + nigh.
well-off (adj.): 1733, "comfortable," from well (adv.) + off. Meaning "prosperous, not poor" is recorded from 1849.
well-ordered (adj.): c.1600, from well (adv.) + past participle of order.
well-read (adj.): 1590s, from well (adv.) + read (adj.).
well-rounded (adj.): 1796, from well (adv.) + past participle of round (v.). Figurative sense is from mid-19c.
well-wisher (n.): 1580s, from well (adv.) + agent noun from wish (v.). Well-wishing is recorded from 1560s.
wellaway: mid-13c., alteration (by influence of Scandinavian forms) of Old English wa la wa, literally "woe, lo, woe!" from wa "woe" (see woe).
Wellington (n.): boot so called from 1817, for Arthur, 1st Duke of Wellington (1769-1852), who also in his lifetime had a style of coat, hat, and trousers named for him as well as a variety of apple and pine tree.
wellness (n.): 1650s, from well (adv.) + -ness.
wellspring (n.): Old English welspryng, literal and figurative, see well (n.) + spring (n.2).
Welsh: Old English Wilisc, Wylisc (West Saxon), Welisc, Wælisc (Anglian and Kentish), from Wealh, Walh "Celt, Briton, Welshman, non-Germanic foreigner;" in Tolkien's definition, "common Gmc. name for a man of what we should call Celtic speech," but also applied to speakers of Latin, hence Old High German Walh, Walah "Celt, Roman, Gaulish," and Old Norse Valir "Gauls, Frenchmen" (Danish vælsk "Italian, French, southern"); from Proto-Germanic *Walkhiskaz, from a Celtic name represented by Latin Volcæ (Caesar) "ancient Celtic tribe in southern Gaul." The word survives in Wales, Cornwall, Walloon, walnut, and in surnames Walsh and Wallace. Borrowed in Old Church Slavonic as vlachu, and applied to the Rumanians, hence Wallachia.

Among the English, Welsh was used disparagingly of inferior or substitute things, hence Welsh rabbit (1725), also perverted by folk-etymology as Welsh rarebit (1785).
welt (n.): early 15c., a shoemaker's term, perhaps related to Middle English welten "to overturn, roll over" (c.1300), from Old Norse velta "to roll" (related to welter (v.)). Meaning "ridge on the skin from a wound" is first recorded 1800.
weltanschauung (n.): 1868, from German Weltanschauung, from welt "world" (see world) + anschauung "perception" (related to English show).
welter (v.): "to roll or twist," c.1300, from Middle Dutch or Middle Low German welteren "to roll," from Proto-Germanic *waltijanan (cf. Old English wieltan, Old Norse velta, Old High German walzan "to turn, revolve," German wälzen "to roll," Gothic waltjan "to roll"), from PIE root *wel- "to turn, revolve" (see vulva). The noun meaning "confused mass" is first recorded 1851.
welterweight (n.): 1832, "heavyweight horseman," later "boxer or wrestler of a certain weight" (1896), from earlier welter "heavyweight horseman or boxer" (1804), possibly from welt (v.) "beat severely" (c.1400).
weltschmerz (n.): "pessimism about life," 1875, from German Weltschmerz, coined 1810 by Jean Paul Richter, from Welt "world" + Schmerz "pain." Popularized in German by Heine.
wen (n.): Old English wenn "a wen, wart," a West Germanic word (cf. Middle Low German wene, Dutch wen, dialectal German Wenne) of uncertain origin.
Wenceslas: masc. proper name, from Medieval Latin Venceslaus (modern Czech Vaclav), from Old Czech Veceslavu, literally "having greater glory," from Slavic *vetye- "greater" + *-slavu "fame, glory," from PIE *klou-, from root *kle- "to hear" (see listen).
wench (n.): late 13c., wenche "girl or young woman," shortened from wenchel "child" (12c.), from Old English wencel, probably related to wancol "unsteady, fickle, weak," and cognate with Old Norse vakr "child, weak person," Old High German wanchal "fickle." The word degenerated through being used in reference to servant girls, and by mid-14c. was being used in a sense of "woman of loose morals, mistress."
The wenche is nat dead, but slepith. [Wyclif, Matt. ix:24, c.1380]
wench (v.): "to associate with common women," 1590s, from wench (n.). Related: Wenched; wenching.
wend (v.): "to proceed on," Old English wendan "to turn, go," from Proto-Germanic *wandijanan (cf. Old Saxon wendian, Old Norse venda, Old Frisian wenda, Dutch wenden, German wenden, Gothic wandjan "to turn"), causative of Old English windan "to turn, twist" (see wind (v.)), from root *wand-, *wend- "turn." Surviving only in to wend one's way, and in hijacked past tense form went.
Wend: member of a Slavic people of eastern Germany, 1610s (implied in Wendish), from German Wende, from Old High German Winida, related to Old English Winedas "Wends," ultimately from Celt. *vindo- "white."