Online Etymology Dictionary

acropolis: 1660s, from Gk. akropolis "citadel" (especially that of Athens), from akros "highest, upper" (see acrid) + polis "city" (see policy (1)).
across: c.1300, from Anglo-Fr. an cros "in a crossed position," lit. "on cross." Prepositional meaning "from one side to another" is first recorded 1590s; meaning "on the other side (as a result of crossing)" is from 1750. Phrase across the board originally from horse-racing, in reference to a bet of the same amount of money on a horse to win, place, or show.
acrostic: short poem in which the initial letters of the lines, taken in order, spell a word or phrase, 1580s, from M.L. acrostichis, from Gk. akrostikhis, from akros "at the end, outermost" (see acrid) + stikhos "line of verse," lit. "row" (see stair).
acrylic (adj.): 1855, "of or containing acryl," a substance derived from garlic and onion, from acrolein, from L. acer "sharp" (see acrid) + olere "to smell" (see odor). Modern senses often short for acrylic fiber, resin, etc.
act (n.): late 14c., from O.Fr. acte, from L. actus "a doing" and actum "a thing done," both from agere "to do, set in motion, drive, urge, chase, stir up," from PIE root *ag- "to drive, draw out or forth, move" (cf. Gk. agein "to lead, guide, drive, carry off," agon "assembly, contest in the games," agogos "leader;" Skt. ajati "drives," ajirah "moving, active;" O.N. aka "to drive;" M.Ir. ag "battle"). Theatrical (1510s) and legislative (mid-15c.) senses of the word also were in Latin. The verb is first attested late 15c.; in the theatrical performance sense it is from 1590s. In the act "in the process" is from 1590s, originally from the 16c. sense of the act as "sexual intercourse." Act of God "uncontrollable natural force" first recorded 1882. To act out "behave anti-socially" (1974) is from psychiatric sense of "expressing one's unconscious impulses or desires."
acting: 1590s, verbal noun or prp. adj. from act (q.v.); acting out in psychology is from 1945.
action: mid-14c., from O.Fr. action (12c.), from L. actionem (nom. actio), from pp. stem of agere "to do" (see act). Meaning "fighting" is from c.1600. As a film director's command, it is attested from 1923. Meaning "excitement" is recorded from 1968. Phrase actions speak louder than words is attested from 1845. Related: Actionable (1590s).
active: mid-14c., from L. activus, from actus (see act). Active voice is recorded from 1765 (grammatical use of active dates from 1520s). Related: Activate (v. 1620s).
activist: "one who advocates a doctrine of direct action," 1915; from active (q.v.). Activism in this sense is first attested 1920; earlier (1907) it was used in ref. to a philosophical theory.
activity: 1540s, "state of being active," from Fr. activité, from M.L. activitatem (nom. activitas), a word in Scholastic philosophy, from L. activus (see active). Meaning "state of being active, briskness, liveliness" recorded from 1520s. Activities in schoolwork sense is from 1923, Amer. Eng.
actor: late 14c., "an overseer, a plaintiff," from L. actor "an agent or doer," from pp. stem of agere (see act). Sense of "one who performs in plays" is 1580s, originally applied to both men and women.
actress: 1580s, "female who does something;" see actor; stage sense is from 1700. Sometimes Fr. actrice was used.
Acts: short for "Acts of the Apostles" in NT, from 1530s.
actual: early 14c., "pertaining to an action," from O.Fr. actuel "now existing, up to date" (13c.), from L.L. actualis "active," adj. form of L. actus (see act). The broader sense of "real" (as opposed to potential, ideal, etc.) is due to infl. of Fr. actualite.
actualize: 1810, first attested in Coleridge, from actual (q.v.) + -ize.
actually: late 15c., "actively," from actual (q.v.). Meaning "in fact, as opposed to possibility" is from 1580s; that of "at this time, at present" is from 1660s. As an intensive added to a statement and suggesting "as a matter of fact, really, in truth" it is attested from 1762.
"Mod. use of actuality in the sense of realism, contact with the contemporary, is due to Fr. actualité, from actuel, which does not mean actual, real, but now existing, up to date." [Weekley]
actuary: 1550s, "registrar, clerk," from L. actuarius "copyist, account-keeper," from actus "public business" (see act). Modern insurance office meaning first recorded 1849. Related: Actuarial (1869).
acuity: 1540s, from M.Fr. acuité, from M.L. acuitatem (nom. acuitas) "sharpness," from L. acus "needle," acuere "to sharpen," from PIE base *ak- "rise to a point, be sharp" (see acrid).
acumen: 1530s, from L. acumen "a point, sting," hence "sharpness, shrewdness," from acuere "to sharpen" (see acuity).
acupuncture: 1680s, "pricking with a needle" to ease pain, from L. acus "needle" (see acuity) + Eng. puncture. The verb is first recorded 1972.
acute: 1560s, from L. acutus "sharp, pointed," pp. of acuere "sharpen" (see acuity). Medical sense of "coming and going quickly" (of a fever or disease, as opposed to a chronic one) first recorded 1660s.
ad: 1841, shortened form of advertisement. Long resisted by those in the trade, and denounced 1918 by the president of a national advertising association as "the language of bootblacks, ... beneath the dignity of men of the advertising profession."
ad hoc: 1650s, from L., lit. "for this (specific purpose)."
ad hominem: c.1600, from L., lit. "to a man," from ad "to" + hominem, acc. of homo "man."
ad infinitum: 1670s, from L., from ad "to" + infinitum "infinity," neut. of adj. infinitus "endless" (see infinite).
ad lib: 1811, from L. ad libitum "at one's pleasure, as much as one likes" (c.1600), from libere "to please." First recorded as one word 1919 (v.), 1925 (n.).
ad nauseam: "to a sickening extent," 1610s, from L., lit. "to sickness."
ad valorem: type of customs duties, 1711, L. "in proportion to the value."
ad-: prefix expressing direction toward or in addition to, from L. ad "to, toward," from PIE *ad- "to, near, at" (cognate with O.E. æt; see at). Simplified to a- before sc-, sp- and st-; modified to ac- before many consonants and then re-spelled af-, ag-, al- etc., in conformity with the following consonant (e.g. affection, aggression). In O.Fr., reduced to a- in all cases, but written forms were refashioned after L. in 14c. in Fr., and 15c. in Eng. words picked up from O.Fr. In many cases pronunciation followed the shift.
Ada: fem. proper name, from Heb. Adha, lit. "ornament."
adage: 1540s, from L. adagium "adage, proverb," apparently from adagio, from ad- "to" + *agi-, root of aio "I say," from PIE *ag- "to speak." But Tucker thinks the second element is rather ago "set in motion, drive, urge."
adagio: c.1746 (adv.) "slowly, leisurely," from It., from ad- "to, at" + agio "leisure," from V.L. adjacens, prp. of adjacere "to lie at, to lie near" (cf. ease, adjacent). In musical sense of "a slow movement" (n.), first attested 1784.
Adam: Biblical name of the first man, from Heb. adam "man," lit. "(the one formed from the) ground" (Heb. adamah "ground"); cf. L. homo "man," humanus "human," humus "earth, ground, soil." Adam's apple (1755) perhaps is an inexact translation of Heb. tappuah haadam, lit. "man's swelling," from ha-adam "the man" + tappuah "anything swollen." The allusion is to the fact that a piece of the forbidden fruit (commonly believed to be an apple) that Eve gave Adam is supposed to have stuck in his throat. To not know (someone) from Adam "not know him at all" is first recorded 1784.
adamant (adj.): late 14c., "hard, unbreakable," from earlier noun (O.E. aðamans) meaning "a very hard stone," from L. adamantem (nom. adamas), from Gk. adamas (gen. adamantos) "unbreakable," the name of a hypothetical hardest material, perhaps lit. "invincible," from a- "not" + daman "to conquer, to tame" (see tame), or else a word of foreign origin altered to conform to Gk. Applied in antiquity to white sapphire, magnet (perhaps via confusion with L. adamare "to love passionately"), steel, emery stone, and especially diamond (see diamond). Figurative sense of "unshakeable" first recorded 1670s.
adamantine (adj.): late 14c., from L. adamantinus, from Gk. adamantinos, from adamas (see adamant).
adapt: c.1600 (implied in adapted) "to fit (something, for some purpose)," from M.Fr. adapter (14c.), from L. adaptare "adjust," from ad- "to" + aptare "join," from aptus "fitted" (see apt). Meaning "to undergo modification so as to fit new circumstances" (intr.) is from 1956.
adaptation: c.1600, "action of adapting," from Fr. adaptation, from L.L. adaptationem (nom. adaptatio), noun of action from adaptare (see adapt). Meaning "condition of being adapted" is from 1670s. Sense of "modification of a thing to suit new conditions" is from 1790. Biological sense first recorded 1859 in Darwin's writings.
add: late 14c., from L. addere "add to, join" from ad- "to" + -dere comb. form meaning "to put, place," from dare "to give" (see date (1)). To add up "make sense" is from 1942. Add-on "additional component" is from 1941.
addendum: 1794, "something added," from L. neut. of addendus "that which is to be added," gerundive of addere (see add). Plural form is addenda.
adder: O.E. næddre "a snake," from W.Gmc. *nædro "a snake" (cf. O.N. naðra, M.Du. nadre, Ger. Natter, Goth. nadrs), from PIE base *netr- (cf. L. natrix "water snake," probably by folk-association with nare "to swim;" O.Ir. nathir, Welsh neidr "adder"). The modern form represents a faulty separation 14c.-16c. into an adder, for which see also apron, auger, nickname, humble pie, umpire. Nedder is still a northern Eng. dialect form. Folklore connection with deafness is via Psalm lviii.1-5. The adder is said to stop up its ears to avoid hearing the snake charmer called in to drive it away, though whether this tradition can account for the O.T. reference I cannot say. Adder-bolt (late 15c.) was a former name for "dragonfly."
addict: 1520s, adj., "delivered, devoted," from L. addictus, pp. of addicere "to deliver, award, yield, devote," from ad- "to" + dicere "say, declare" (see diction), but also "adjudge, allot." Modern sense is really self-addicted "to give over or award (oneself) to someone or some practice" (c.1600); specialization to narcotics dependency is from c.1910. The noun is first recorded 1909, in reference to morphine. Related: Addicted (1530s, "delivered over" by judicial sentence; modern meaning "dependent on a drug" from 1913); adj. addictive (1939 in the narcotics sense).
addiction: c.1600, of habits, pursuits, etc., from L. addictionem (nom. addictio) "an awarding, a devoting," noun of action from addicere (see addict). Earliest sense was less severe: "inclination, penchant," but this has become obsolete. In main modern sense it is first attested 1906, in ref. to opium (there is an isolated instance from 1779, with ref. to tobacco).
addition: mid-14c., "that which is added," from O.Fr. addition (13c.), from L. additionem (nom. additio) "an adding to, addition," from additus, pp. of addere (see add). Meaning "action of adding" first attested mid-15c. Phrase in addition to "also" is from 1902. Related: Additional (1640s).
additive: 1690s, adj., "tending to be added," from L. additivus "added, annexed," from pp. stem of addere (see addition). Noun meaning "something that is added" to a chemical solution or food product is recorded from 1945.
addle (v.): 1712, from addle (n.) "urine, liquid filth," from O.E. adela "mud, mire, liquid manure" (cognate with O.Swed. adel "urine," M.L.G. adel, Du. aal "puddle"). Used in noun phrase addle egg (mid-13c.) "egg that does not hatch, rotten egg," lit. "urine egg," a loan-transl. of L. ovum urinum, which is itself an erroneous loan-transl. of Gk. ourion oon "putrid egg," lit. "wind egg," from ourios "of the wind" (confused by Roman writers with ourios "of urine," from ouron "urine"). Because of this usage, the noun in Eng. was taken as an adj. from c.1600, meaning "putrid," and thence given a fig. extension to "empty, vain, idle," also "confused, muddled, unsound" (1706). The verb followed.
address (v.): late 14c., "to make straight," from O.Fr. adresser (13c.), from V.L. *addirectiare "make straight," from L. ad "to" + *directiare, from L. directus "straight, direct" (see direct). Meaning "to direct spoken words (to someone)" is from late 15c.; noun sense of "formal speech" is from 1751. Meaning in English expanded 17c.-18c. to the notion of directing something, as a letter, "straight" to where somebody lives. "To send as a written message" is from 1630s, which led to noun senses of "superscription of a letter" (1712) and "place of residence" (1888). Related: Addressee (1810).
adduce: 1610s, from L. adducere "lead to, bring to," from ad- "to" + ducere "to lead" (see duke).
Adelaide: fem. proper name, from Fr. Adélaide, from a Gmc. source, cf. O.H.G. Adalhaid, from adal "noble family" + heit "state, rank," related to O.E. -had "person, degree, state, nature" (see -hood). The first element + Fr. fem. ending -ine gave the fem. proper name Adeline.
Adelphia: district of London, so called because it was laid out by four brothers of a family named Adam, from Gk. adelphos "brother," lit. "from the same womb," from copulative prefix a- "together with" + delphys "womb," perhaps related to dolphin (q.v.). The district was the site of a popular theater c.1882-1900, which gave its name to a style of performance.
Aden: place in southern Arabia, ult. from Akkad. edinnu "plain," which some think is also is the root of Biblical Eden.