Online Etymology Dictionary

a (1): indefinite article, mid-12c., a variation of Old English an (see an) in which the -n- began to disappear before consonants, a process mostly complete by mid-14c. The -n- also was retained before words beginning with a sounded -h- until c. 1600; it still is retained by many writers before unaccented syllables in h- or (e)u-, but is now no longer normally spoken as such. The -n- also lingered (especially in southern England dialect) before -w- and -y- through 15c.
a (2): as in twice a day, etc., from Old English an "on," in this case "on each." The sense was extended from time to measure, price, place, etc. The habit of tacking a onto a gerund (as in a-hunting we will go) died out 18c.
a capella: 1876, earlier alla capella (1847), from Italian, "in the manner of the chapel," literally "according to the chapel," from cappella "chapel" (see chapel). Originally in reference to older church music (pre-1600) which was written for unaccompanied voices; applied 20c. to unaccompanied vocal music generally.
a deux: French, à deux, literally "for two" (see deuce).
a la: from French à la, "in the manner of;" used in English in French terms from fashion or cookery since late 16c.; used in native formations with English words or names from c. 1800 (first attested in Jane Austen).
a la carte: 1826, from French à la carte, literally "by the card" (see card (n.1)); in other words, "ordered by separate items." Distinguished from a table d'hôte, meal served at a fixed, inclusive price.
a la mode: 1640s, from French à la mode (15c.), literally "in the fashion" (see mode (n.2)). In 17c., sometimes nativized as all-a-mode. Cookery sense of a dessert served with ice cream is 1903, American English.
a posteriori: Latin, literally "from what comes after" (see posterior).
a priori: 1710, "from cause to effect" (a logical term, in reference to reasoning), Latin, literally "from what comes first," from priori, ablative of prior "first" (see prior (adj.)). Used loosely for "in accordance with previous knowledge" (1834).
A&P: U.S. grocery chain, originally The Great Atlantic and Pacific Tea Company, founded 1859 by George Huntington Hartford and George Gilman.
a- (1): in native (derived from Old English) words, it most commonly represents Old English an "on" (see a (2)), as in alive, asleep, abroad, afoot, etc., forming adjectives and adverbs from nouns; but it also can be Middle English of, as in anew, abreast (1590s); or a reduced form of Old English past participle prefix ge-, as in aware; or the Old English intensive a-, as in arise, awake, ashame, marking a verb as momentary, a single event. In words from Romanic languages, often it represents Latin ad- "to, at."
[I]t naturally happened that all these a- prefixes were at length confusedly lumped together in idea, and the resultant a- looked upon as vaguely intensive, rhetorical, euphonic, or even archaic, and wholly otiose. [OED]
a- (2): prefix meaning "not," from Latin a-, short for ab "away from" (as in avert); see ab-.
a- (3): prefix meaning "not," from Greek a-, an- "not," from PIE root *ne "not" (see un-).
A-1: in figurative sense of "first-rate," 1837, in Dickens; from Lloyd's of London designation for ships in first-class condition (with the letter referring to the condition of the ship and the number to that of the stores).
A-frame: type of framework shaped like the letter "A," 1909; as a type of building construction from 1932.
A-line (adj.): descriptive of a dress or skirt flared in shape of a letter "A," 1955, in reference to the designs of Christian Dior (1905-1957).
A-list (adj.): in celebrity sense, 1984, from A in the sense of "first, best" (as in A-1) + list (n.1).
A-OK: 1961, said to be an abbreviation of all (systems) OK; popularized in the jargon of U.S. astronauts. See OK.
A.A.: also AA, abbreviation of Alcoholics Anonymous, attested by 1941, American English. The group name was the title of a book published in 1938 by the founder, Bill W.
A.A.A.: also AAA, abbreviation of American Automobile Association, attested 1902, American English, the year the organization was founded.
A.D.: 1570s, from Latin Anno Domini "Year of the Lord." Put forth by Dionysius Exiguus in 527 or 533 C.E., but used at first only for Church business. Introduced in Italy in 7c., France (partially) in 8c. In England, first found in a charter of 680 C.E. Ordained for all ecclesiastical documents in England by the Council of Chelsea, July 27, 816.

The resistance to it in part might have come because Dionysius chose 754 A.U.C. as the birth year of Jesus, while many early Christians would have thought it was 750 A.U.C. (See John J. Bond, "Handy-Book of Rules and Tables for Verifying Dates With the Christian Era," 4th ed., London: George Bell & Sons, 1889.) A.C., for Anno Christi, also was common 17c.
a.k.a.: also aka, initialism (acronym) for also known as; attested in legal documents from at least 1936.
a.m.: in reference to hours, 1762, abbreviation of Latin ante meridiem "before noon."
A.M.: also AM, type of radio wave broadcast, 1921, abbreviation of amplitude modulation.
A.P.R.: also APR, abbreviation of annual percentage rate, attested from 1979, American English.
a.s.a.p.: also asap, pronounced either as a word or as four letters, 1955, from initial letters of phrase as soon as possible; originally U.S. Army jargon.
A.V.: abbreviation of Authorized Version (of the English Bible, 1611) attested from 1868.
aardvark (n.): 1833, from Afrikaans Dutch aardvark, literally "earth-pig" (the animal burrows), from aard "earth" (see earth) + vark "pig," cognate with Old High German farah (source of German Ferkel "young pig, sucking pig," a diminutive form), Old English fearh (see farrow).
Aaron: masc. proper name, in the Old Testament the brother of Moses, from Hebrew Aharon, probably of Egyptian origin. The Arabic form is Harun. Aaron's beard as a type of herb is from 1540s.
ab initio: c. 1600, Latin, literally "from the beginning," from ab "from" + oblique case of initium "entrance, beginning," related to verb inire "to go into, enter upon, begin" (see initial).
ab-: word-forming element meaning "away, from, from off, down;" from Latin ab-, ab "off, away from," cognate with Greek apo "away from, from," Sanskrit apa "away from," Gothic af, Old English of, from PIE root *apo- (see apo-). Reduced to a- before -m-, -p-, or -v-; sometimes abs- before -c- or -t-.
aback (adv.): c. 1200, from Old English on bæc "at or on the back;" see back (n.). Now surviving mainly in taken aback, originally a nautical expression in reference to a vessel's square sails when a sudden change of wind flattens them back against the masts and stops the forward motion of the ship (1754). The figurative sense is first recorded 1840.
abacus (n.): late 14c., "sand table for drawing, calculating, etc.," from Latin abacus, from Greek abax (genitive abakos) "counting table," from Hebrew abaq "dust," from root a-b-q "to fly off." Originally a drawing board covered with dust or sand that could be written on to do mathematical equations. Specific reference to a counting frame is 17c. or later.
Abaddon: late 14c., used in Rev. ix:11 of "the angel of the bottomless pit," and by Milton of the pit itself, from Hebrew Abhaddon "destruction," from abhadh "he perished." The Greek form was Apollyon.
abaft (adv.): "in or at the back part of a ship" (opposed to forward), 1590s, from Middle English on baft (Old English on bæftan) "backwards." The second component is itself a compound of be "by" (see by) and æftan "aft" (see aft). The word has been saved by the sailors (the stern being the "after" part of a vessel), the rest of the language having left it in Middle English.
abalienate (v.): 1550s, from Latin abalienatus, past participle of abalienare "to remove, literally "to make alien," from ab- (see ab-) + alienare (see alienate). Related: Abalienated; abalienating.
abalienation (n.): 1650s, from Latin abalienationem (nominative abalienatio), noun of action from past participle stem of abalienare (see abalienate).
abalone (n.): type of marine shell, 1850, American English, from Spanish abulon from Costanoan (a California coastal Indian language family) aluan "red abalone."
abandon (v.): late 14c., "to give up, surrender (oneself or something), give over utterly; to yield (oneself) utterly (to religion, fornication, etc.)," from Old French abandoner (12c.), from adverbial phrase à bandon "at will, at discretion," from à "at, to" (see ad-) + bandon "power, jurisdiction," from Latin bannum, "proclamation," from a Frankish word related to ban (v.).
Mettre sa forest à bandon was a feudal law phrase in the 13th cent. = mettre sa forêt à permission, i.e. to open it freely to any one for pasture or to cut wood in; hence the later sense of giving up one's rights for a time, letting go, leaving, abandoning. [Auguste Brachet, "An Etymological Dictionary of the French Language," transl. G.W. Kitchin, Oxford, 1878]
Etymologically, the word carries a sense of "put someone under someone else's control." Meaning "to give up absolutely" is from late 14c. Related: Abandoned; abandoning.
abandon (n.): "a letting loose, surrender to natural impulses," 1822, from a sense in French abandon (see abandon (v.). Borrowed earlier (c. 1400) from French in a sense "(someone's) control;" and compare Middle English adverbial phrase at abandon, i.e. "recklessly," attested from late 14c.
abandoned (adj.): "self-devoted" to some purpose (usually evil), late 14c., past participle adjective from abandon (v.).
abandonment (n.): 1610s, from French abandonnement, from abandonner (see abandon (v.)).
abase (v.): late 14c., abaishen, from Old French abaissier "diminish, make lower in value or status" (12c.), from Vulgar Latin *ad bassiare "bring lower," from ad- "to" (see ad-) + Late Latin bassus "thick, fat, low" (see base (adj.)). Form in English altered 16c. by influence of base (adj.), thus the word is an exception from the rule that Old French verbs with stem -iss- enter English as -ish. Related: Abased; abasing.
abasement (n.): early 15c., "embarrassment, dread, fear," from abase + -ment. Sense of "action of lowering in price" is mid-15c.; "action of lowering in rank" is 1560s; "condition of being abased" is from 1610s.
abash (v.): "perplex, embarrass," early 15c., earlier "lose one's composure, be upset" (late 14c.), from Old French esbaiss-, present stem of esbaer "gape with astonishment," from es "out" (see ex-) + ba(y)er "to be open, gape," from Latin *batare "to yawn, gape," from root *bat, possibly imitative of yawning. Related: Abashed; abashing. Bashful is a 16c. derivative.
abate (v.): c. 1300, "put an end to;" early 14c., "to grow less, diminish in power or influence," from Old French abattre "beat down, cast down," from Vulgar Latin *abbatere, from Latin ad "to" (see ad-) + battuere "to beat" (see batter (v.)). Secondary sense of "to fell, slaughter" is in abatis and abattoir. Related: Abated; abating.
abatement (n.): mid-14c., from Old French abatement, from abattre (see abate).
abatis (n.): "defense made of felled trees," 1766, from French abatis, literally "things thrown down," from Old French abateis, from abattre "to beat down, throw down" (see abate).
abattoir (n.): "slaughterhouse for cows," 1820, from French abattre "to beat down" (see abate) + suffix -oir, corresponding to Latin -orium (see -ory).
ABBA: Swedish pop music group formed 1972, the name dates from 1973 and is an acronym from the first names of the four band members: Anni-Frid Lyngstad, Björn Ulvaeus, Benny Andersson, Agnetha Fältskog.