Online Etymology Dictionary

astronautics (n.): 1929, see astronaut + -ics.
astronomer (n.): late 14c., from astronomy (q.v.), replacing French import astronomyen (c. 1300), which, had it survived, probably would have yielded *astronomian. Still in Shakespeare used in places where we would write astrologer.
astronomical (adj.): 1550s, from astronomy + -ical. Popular meaning "immense, concerning very large figures" (as sizes and distances in astronomy) is attested from 1899. Astronomical unit (abbreviation A.U.) "mean distance from Earth to Sun," used as a unit of measure of distance in space, is from 1909. Related: Astronomically.
astronomy (n.): c. 1200, from Old French astrenomie, from Latin astronomia, from Greek astronomia, literally "star arrangement," from astron "star" (see astro-) + nomos "arranging, regulating," related to nemein "to deal out" (see numismatic). Used earlier than astrology and originally including it.
Þer wes moni god clarc to lokien in þan leofte, to lokien i þan steorren nehʒe and feorren. þe craft is ihate Astronomie. [Layamon, "The Brut," c. 1200]
astrophotography (n.): 1858, from astro- + photography.
astrophysicist (n.): 1869, usually hyphenated at first, from astro- + physicist. Astrophysics is recorded from 1877.
Astroturf (n.): 1966, proprietary name for a kind of artificial grass, so called because it was used first in the Houston, Texas, Astrodome, indoor sports stadium. See astro- + turf. Houston was a center of the U.S. space program.
astute (adj.): 1610s, from Latin astutus "crafty, wary, shrewd; sagacious, expert," from astus "cunning, cleverness, adroitness," which is of uncertain origin, perhaps from Greek asty "town," a word borrowed into Latin and with an overtone of "city sophistication" (compare asteism). Related: Astutely; astuteness.
Astyanax: son of Hector and Andromache ("Iliad"), Greek, literally "lord of the city," from asty "city" (see asteism) + anax "chief, lord, master." Also the epithet of certain gods.
asunder (adv.): mid-12c., contraction of Old English on sundran (see sunder). Middle English used to know asunder for "distinguish, tell apart."
asylum (n.): early 15c., earlier asile (late 14c.), from Latin asylum "sanctuary," from Greek asylon "refuge," noun use of neuter of asylos "inviolable, safe from violence," especially of persons seeking protection, from a- "without" + syle "right of seizure." So literally "an inviolable place." General sense of "safe or secure place" is from 1640s; meaning "benevolent institution to shelter some class of persons" is from 1776.
asymmetrical (adj.): 1680s; see asymmetry + -ical. Other forms that have served as an adjective based on asymmetry are asymmetral (1620s), asymmetrous (1660s), and asymmetric (1875); only the last seems to have any currency. Related: Asymmetrically.
asymmetry (n.): 1650s, "want of symmetry or proportion," from Greek asymmetria, noun of quality from asymmetros "having no common measure; disproportionate, unsymmetrical," from a- "not" + symmetros "commensurable" (see symmetry).
asymptomatic (adj.): "without symptoms," 1856, from a-, privative prefix, + symptomatic.
asymptote (n.): "straight line continually approaching but never meeting a curve," 1650s, from Greek asymptotos "not falling together," from a- "not" + syn "with" + ptotos "fallen," verbal adjective from piptein "to fall" (see symptom). Related: Asymptotic.
asymptotic (adj.): 1670s, see asymptote + -ic. Related: Asymptotical; asymptotically.
asynchronous (adj.): 1748, from a-, privative prefix, + synchronous.
asyndetic (adj.): 1823; see asyndeton + -ic.
asyndeton (n.): "omission of conjunctions," 1580s, from Latin, from Greek asyndeton, neuter of asyndetos "unconnected," from a-, privative prefix (see a- (3)), + syndetos, from syndein "to bind together," from syn- "together" (see syn-) + dein "to bind," related to desmos "band," from PIE *de- "to bind."
asystole (n.): 1860, from Modern Latin, from Greek a-, privative prefix (see a- (3)), + systole "contraction" (see systole).
at (prep.): Old English æt, from Proto-Germanic *at (source also of Old Norse, Gothic at, Old Frisian et, Old High German az), from PIE *ad- "to, near, at" (source also of Latin ad "to, toward" Sanskrit adhi "near;" see ad-).

Lost in German and Dutch, which use their equivalent of to; in Scandinavian, however, to has been lost and at fills its place. In choosing between at church, in church, etc. at is properly distinguished from in or on by involving some practical connection; a worshipper is at church; a tourist is in the church.

The colloquial use of at after where ("where it's at") is attested from 1859. At last is recorded from late 13c.; adverbial phrase at least was in use by 1775. At in Middle English was used freely with prepositions (as in at after, which is in Shakespeare), but this has faded with the exception of at about, which was used in modern times by Trollope, Virginia Woolfe, D.H. Lawrence, and Evelyn Waugh, but nonetheless is regarded as a sign of incompetent writing by my copy editor bosses.
at all: "in any way," mid-14c., originally used only affirmatively (as in I Sam. XX:6 in KJV: "If thy father at all misse me"); now it is overwhelmingly used only in the negative or in interrogatory expressions, or in literary attempts at Irish dialect.
at bay: late 14c., originally often at the bay; see bay (n.3). Figurative use, of human beings in difficulties, is from c. 1400. The expression reflects the former more widespread use of at. Earlier the expression be at abai was used of the hunted animal, "be unable to escape," c. 1300, from French.
at-: assimilated form of ad- "to, toward, before" before stems beginning in -t-; see ad-.
at-bat (n.): "baseball player's turn at the plate," 1912, originally a column heading in statistics tables.
at-home (n.): "reception of visitors," 1745, from phrase at home.
Atalanta: in Greek mythology the daughter of king Schoeneus, famous for her swiftness, Latin, from Greek Atalante, fem. of atalantos "having the same value (as a man)," from a- "one, together" + talanton "balance, weight, value" (compare talent).
ataractic (adj.): 1941, from Greek ataraktos "not disturbed" (see ataraxia) + -ic.
ataraxia (n.): also Englished as ataraxy, "calmness, impassivity," c. 1600, from Modern Latin, from Greek ataraxia "impassiveness," from a-, privative prefix, + tarassein (Attic tarattein) "to disturb, confuse," from PIE root *dher- (1) "to make muddy, darken."
atavic (adj.): "pertaining to a remote ancestor," 1866, from Latin atavus "ancestor" (see atavism) + -ic.
atavism (n.): 1833, from French atavisme, attested by 1820s, from Latin atavus "ancestor, forefather," from at- perhaps here meaning "beyond" + avus "grandfather," from PIE *awo- "adult male relative other than the father" (see uncle).
atavistic (adj.): "pertaining to atavism," 1847; see atavism + -ic.
ataxia (n.): also Englished as ataxy, "irregularity of bodily functions," 1610s, "confusion, disorder," medical Latin, from Greek ataxia, from a-, privative prefix, + taxis "arrangement, order," from stem of tassein "to arrange" (see tactics). Pathological sense is attested from 1660s.
ataxic (adj.): 1853, from ataxia + -ic.
atchoo: imitative of the sound of sneezing, first attested 1873, as atcha (a-tschoo is from 1878).
ate: past tense of eat (q.v.).
Ate: Greek goddess of infatuation and evil, from ate "infatuation, bane, ruin, mischief," which is of uncertain origin.
atelectasis (n.): "incomplete expansion of the lungs," 1836, medical Latin, from Greek ateles "imperfect, incomplete," literally "without an end," (from a-, privative prefix, + telos "completion") + ektosis "extention." Related: Atelectatic.
atelier (n.): 1840, from French atelier "workshop," from Old French astelier "(carpenter's) workshop, woodpile" (14c.), from astele "piece of wood, a shaving, splinter," probably from Late Latin hastella "a thin stick," diminutive of hasta "spear, shaft" (see yard (n.2)).
atemporal (adj.): 1870, from a- "not" + temporal. Related: Atemporally.
Aten: a name of the sun in ancient Egypt, from Egyptian itn.
Athabascan: 1846, Athapaskan, from the name of the North American Indian people, from Lake Athabaska in northern Alberta, Canada, from Woods Cree (Algonquian) Athapaskaw, said by Webster to mean literally "grass or reeds here and there," referring to the delta region west of the lake. Also in reference to their language group.
Athanasian (adj.): 1580s, from Athanasius, archbishop of Alexandria in the reign of Constantine. The name is Latin, from Greek Athanasios, from athanatos "immortal," from a- "not," privative prefix, + thanatos "death" (see thanatology).
atheism (n.): 1580s, from French athéisme (16c.), from Greek atheos "without god" (see atheist). A slightly earlier form is represented by atheonism (1530s) which is perhaps from Italian atheo "atheist." Ancient Greek atheotes meant "ungodliness."
atheist (n.): 1570s, from French athéiste (16c.), from Greek atheos "without god, denying the gods; abandoned of the gods; godless, ungodly," from a- "without" + theos "a god" (see theo-).
The existence of a world without God seems to me less absurd than the presence of a God, existing in all his perfection, creating an imperfect man in order to make him run the risk of Hell. [Armand Salacrou, "Certitudes et incertitudes," 1943]
atheistic (adj.): 1630s, from atheist + -ic. Atheistical attested from c. 1600.
atheling (n.): "member of a noble family," Old English æðling, from æðel "noble family," related to Old English æðele "noble," from Proto-Germanic *athala-, from PIE *at-al- "race, family," from *at(i)- "over, beyond, super" + *al- "to nourish." With suffix -ing "belonging to." A common Germanic word (cognates: Old Saxon ediling, Old Frisian etheling, Old High German adaling).
Athelstan: masc. proper name, Old English Æðelstane, literally "noble stone;" see atheling + stone (n.).
Athena: Greek goddess of wisdom, skill in the arts, warfare, etc., from Latin Athena, from Greek Athene, perhaps from a name in a lost pre-Hellenic language.
Athenaeum (n.): 1727, from Latinized form of Greek Athenaion "the temple of Athene," in ancient Athens, in which professors taught and actors or poets rehearsed. Meaning "literary club-room or reading room" is from 1799; "literary or scientific club" is from 1864.