Online Etymology Dictionary

as (adv.): c. 1200, worn-down form of Old English alswa "quite so" (see also), fully established by c. 1400. Equivalent to so; any distinction in use is purely idiomatic. Related to German als "as, than," from Middle High German also. Phrase as well "just as much" is recorded from late 15c.; the phrase also can imply "as well as not," "as well as anything else." Interjection of incredulity as if! (i.e. "as if that really could happen") is attested from 1995, an exact duplication of Latin quasi.
asafetida (n.): late 14c., from Medieval Latin asa (Latinized from Persian aza "mastic") + foetida, fem. of foetidus "stinking" (see fetid).
asafoetida (n.): alternative spelling of asafetida (q.v.); also see oe.
asap: see a.s.a.p.
asbestine (adj.): 1620s, from Latin asbestinus, from Greek asbestinos, from asbestos (see asbestos).
asbestos (n.): 1650s, earlier albeston, abestus (c. 1100), name of a fabulous stone, which, set afire, could not be extinguished; from Old French abeste, abestos, from Latin asbestos "quicklime" (which "burns" when cold water is poured on it), from Greek asbestos, literally "inextinguishable," from a- "not" (see a- (3)) + sbestos, verbal adjective from sbennynai "to quench," from PIE root *(s)gwes- "to quench, extinguish" (source also of Lithuanian gestu "to go out," Old Church Slavonic gaso, Hittite kishtari "is being put out").

The Greek word was used by Dioscorides as a noun meaning "quicklime." "Erroneously applied by Pliny to an incombustible fibre, which he believed to be vegetable, but which was really the amiantos of the Greeks" [OED]. Meaning "mineral capable of being woven into incombustible fabric" is from c. 1600 in English; earlier this was called amiant (early 15c.), from Latin amiantus, from Greek amiantos, literally "undefiled" (so called because it showed no mark or stain when thrown into fire). Supposed in the Middle Ages to be salamanders' wool, and an old name for it in English was fossil linen (18c.). Prester John, the Emperor of India, and Pope Alexander III were said to have had robes or tunics made of it.
ascend (v.): late 14c., from Latin ascendere "to climb up, mount, ascend," figuratively "to rise, reach," from ad- "to" (see ad-) + scandere "to climb" (see scan (v.)). Also in 15c. used with a sense "to mount (a female) for copulation." Related: Ascended; ascending. An Old English word for it was stigan.
ascendance (n.): 1742, from ascend + -ance. Properly "the act of ascending," but used from the start in English as a synonym of ascendancy.
ascendancy (n.): "dominant power or influence," 1712; see ascendant + -cy.
ascendant (adj.): late 14c., ascendent, astrological use is earliest, from Middle French ascendant (noun and adjective) and directly from Latin ascendentem (nominative ascendans), present participle of ascendere "to mount, ascend, go up" (see ascend). Sense "moving upward, rising" is recorded from 1590s. In the ascendant "ruling, dominant" (not, as is often thought, "rising") is from 1670s.
ascendency (n.): alternative spelling of ascendancy (see -ance).
ascension (n.): c. 1300, "ascent of Christ into Heaven on the 40th day after the Resurrection," from Latin ascensionem (nominative ascensio) "a rising," noun of action from past participle stem of ascendere "to mount, ascend, go up" (see ascend). Astronomical sense is recorded late 14c.; meaning "action of ascending" is from 1590s. Related: Ascensional.
ascent (n.): c. 1610, "action of ascending," from ascend on model of descend/descent; "climbing" sense is from 1753.
ascertain (v.): early 15c., "to inform, to give assurance," from Anglo-French acerteiner, Old French acertener "to assure, certify" (13c.), from a "to" (see ad-) + certain "sure, assured" (see certain). Modern meaning of "find out for sure by experiment or investigation" is first attested 1794. Related: Ascertained; ascertaining.
ascertainable (adj.): 1783, from ascertain + -able. Related: Ascertainably.
ascetic (adj.): 1640s, from Greek asketikos "rigorously self-disciplined, laborious," from asketes "monk, hermit," earlier "one who practices an art or trade," from askein "to exercise, train," originally "to train for athletic competition, practice gymnastics, exercise."
ascetic (n.): "one of the early Christians who retired to the desert to live solitary lives of meditation and prayer," 1670s, from ascetic (adj.).
asceticism (n.): 1640s, from ascetic (adj.) + -ism. Sometimes also ascetism (c. 1850).
Ascians (n.): inhabitants of the torrid zone, who "haue the Sunne twice euery yeere in their zenith, and then they make no shaddowes at all" [Nathanael Carpenter, "Geographie Delineated forth in Two Bookes," 1635], from Medieval Latin Ascii, from Greek askioi, from a- "not, without," privative prefix (see a- (3)), + skia "shade, shadow" (see shine (v.)).
ASCII: 1963, initialism (acronym) from "American Standard Code for Information Interchange."
ascites (n.): late 14c., "abdominal dropsy," from Latin ascites, from Greek askites (hydrops), literally "baglike dropsy," from askos "bag, sac."
ascitic (adj.): "afflicted with ascites," 1680s; see ascites + -ic. Related: Ascitical.
Asclepius: god of medicine, Latin, from Greek Asklepios, which is of unknown origin.
ascorbic (adj.): 1933 (in ascorbic acid), from a- (2) + scorb(ut)ic "of scurvy" (from Medieval Latin scorbuticus "scurvy"); originally in reference to Vitamin C, which is an anti-scorbutic. The Latin word is perhaps of German or Dutch origin.
Ascot: village near Windsor, Berkshire; site of fashionable race-meeting. Used attributively for clothes suitable for the event; especially a type of tie (1908). The town name is literally "eastern cottage."
ascribable (adj.): 1670s, from ascribe + -able. Related: Ascribably; ascribability.
ascribe (v.): mid-14c., ascrive, from Old French ascrivre "to inscribe; attribute, impute," from Latin ascribere "to write in, to add to in a writing," from ad- "to" (see ad-) + scribere "to write" (see script (n.)). Spelling restored by 16c. Related: Ascribed; ascribing.
ascription (n.): 1590s, "action of adding in writing;" c. 1600, "attribution of authorship or origin," from Latin ascriptionem (nominative ascriptio) "an addition in writing," noun of action from past participle stem of ascribere (see ascribe).
ascus (n.): "sac in certain fungi," 1830, Modern Latin, from Greek askos "leather bag, wine skin," which is of unknown origin.
asea (adj.): 1858, from a- (1) "on" + sea.
ASEAN: initialism (acronym) for Association of South-East Asian Nations, formed 1967 by Indonesia, Malaysia, the Philippines, Singapore, and Thailand; since expanded to 10 nations.
aseismic (n.): "resistant to earthquake destruction," 1884, from a- (2) "not" + seismic.
aseity (n.): "being by itself," 1690s, from Medieval Latin aseitas "state of being by itself," from Latin a "from" + se "oneself" (see suicide).
asepsis (n.): 1892, from a- (2) "not" + sepsis.
aseptic (adj.): 1859, from a- (2) "not" + septic. As a noun from 1884.
asexual (adj.): 1830, as a term in biology, a hybrid from a- (2) "not" + sexual. In general contexts, attested from 1896.
asexuality (n.): 1877; see asexual + -ity.
asexually (adv.): 1862; see asexual + -ly (2).
Asgard (n.): home of the gods in Norse religion, from Old Norse ass "god," which is related to Old English os, Gothic ans "god" (see Aesir) + Old Norse garðr "enclosure, yard, garden" (see yard (n.1)).
ash (n.1): "powdery remains of fire," Old English æsce "ash," from Proto-Germanic *askon (source also of Old Norse and Swedish aska, Old High German asca, German asche, Gothic azgo "ashes"), from PIE root *ai- (2) "to burn, glow" (source also of Sanskrit asah "ashes, dust," Armenian azazem "I dry up," Greek azein "to dry up, parch," Latin ardus "parched, dry"). Spanish and Portuguese ascua "red-hot coal" are Germanic loan-words.

Symbol of grief or repentance; hence Ash Wednesday (c. 1300), from custom introduced by Pope Gregory the Great of sprinkling ashes on the heads of penitents on the first day of Lent. Ashes meaning "mortal remains of a person" is late 13c., in reference to the ancient custom of cremation.
ash (n.2): type of tree, Old English æsc "ash tree," also "spear made of ash wood," from Proto-Germanic *askaz, *askiz (source also of Old Norse askr, Old Saxon ask, Middle Dutch esce, German Esche), from PIE root *os- "ash tree" (source also of Armenian haci "ash tree," Albanian ah "beech," Greek oxya "beech," Latin ornus "wild mountain ash," Russian jasen, Lithuanian uosis "ash"). Ash was the preferred wood for spear-shafts, so Old English æsc sometimes meant "spear" (as in æsc-here "company armed with spears").
ashamed (adj.): Old English asceamed "feeling shame, filled with shame," past participle of ascamian "to feel shame," from a- intensive prefix + scamian "be ashamed, blush; cause shame" (see shame (v.)). The verb is obsolete, but the past participle lives on. Meaning "reluctant through fear of shame" is c. 1300.
Ashanti (n.): 1705, Asiantines, one of the Akan people of central Ghana; native name. As a language, it is part of the Niger-Congo family.
ashen (adj.): "made of ash wood," c. 1300; see ash (n.2) + -en (2); meaning "ash-colored, whitish-gray, deadly pale" is 1808, from ash (n.1).
Asher: masc. proper name, biblical son of Jacob (also the name of a tribe descended from him), from Hebrew, literally "happy."
asherah (n.): 1863, wooden pillar used as symbol of Canaanite goddess Ashera, a name of unknown origin.
Ashkenazim (n.): (plural) "central and northern European Jews" (as opposed to Sephardim, Jews of Spain and Portugal), 1839, from Hebrew Ashkenazzim, plural of Ashkenaz, eldest son of Gomer (Genesis x:3), also the name of a people mentioned in Jeremiah li:27 (perhaps akin to Greek skythoi "Scythians," compare Akkadian ishkuzai); identified historically with various people; in Middle Ages, with the Germans.
ashlar (n.): late 14c., "square stone for building or paving," from Old French aiseler, from Latin axillaris, from axilla, diminutive of axis "board, plank," which is perhaps not the same axis that means "axle." The stone sense is peculiar to English.
Ashley: fem. proper name, all but unknown before c. 1965; one of the most popular names for girls born in U.S. from c. 1980; evidently inspired by the surname Ashley, Ashleigh (attested from 12c.), which means "clearing among the ash trees," from Old English æsc + leah (see ash (n.2) + lea).
ashore (adv.): 1580s, "toward the shore," from a- (1) + shore (n.). Meaning "on the shore" is from 1630s. Middle English had ashore (late 15c.), but it meant "on a slant," literally "propped up," from shore (v.).