Online Etymology Dictionary

atomies (n.): 1590s, "atoms," also "diminutive beings," from atomy, from Latin atomi, plural of atomus (see atom), but taken as a singular in English and re-pluralized in the native way. Perhaps also in some cases a plural of atomy (from misdivision of anatomy).
atomistic (adj.): 1809, in reference to the classical philosophical doctrine of atomism (1670s); modern philosophical sense (logical atomism) traces to 1914 and Bertrand Russell.
atomization (n.): 1866, noun of action from atomize.
atomize (v.): "reduce to atoms," 1845; "reduce a liquid to a very fine mist," 1865, verb formed from atom + -ize. Related: Atomized; atomizing. Originally in reference to medical treatment for injured or diseased lungs; sense of "to destroy with atomic weapons" is from 1945.
atomizer (n.): 1865, agent noun from atomize.
Aton: variant of Aten.
atonal (adj.): 1922, from a- "not" (see a- (2)) + tonal.
atonality (n.): 1950; see atonal + -ity.
atone (v.): 1550s, from adverbial phrase atonen (c.1300) "in accord," literally "at one," a contraction of at and one. It retains the older pronunciation of one. The phrase perhaps is modeled on Latin adunare "unite," from ad- "to, at" (see ad-) + unum "one." Related: Atoned; atoning.
atonement (n.): 1510s, "condition of being at one (with others)," from atone + -ment. Meaning "reconciliation" (especially of sinners with God) is from 1520s; that of "propitiation of an offended party" is from 1610s.
atop (adv.): 1650s, from a- (1) + top. Two words or hyphenated at first; not fully established as one word till late 19c.
atopic (adj.): 1923, from atopia (see atopy) + -ic.
atopy (n.): 1923, coined by Edward D. Perry, professor of Greek at Columbia University, at the request of medical men, from Greek atopia "unusualness, strangeness, a being out of the way," from atopos "out of place, strange, odd, eccentric," from a-, privative prefix (see a- (3)), + topos "place" (see topos).
ATP: abbreviation of adenosine triphosphate, attested from 1939.
atrabiliary (adj.): 1725, from Medieval Latin atrabilarius; see atrabilious.
atrabilious (adj.): 1650s, from Latin atra bilis, translating Greek melankholia "black bile" (see melancholy; also cf. bile). Atra is fem. of ater "black, dark, gloomy," perhaps related to root of atrocity. Related: Atrabiliousness.
atremble (adv.): 1852, from a- (1) + tremble (v.).
atresia (n.): "occlusion of a natural passage in the body," 1807, from Modern Latin atresia, from Greek atretos "not perforated," from a-, privative prefix, + tresis "perforation," from PIE *tere- "to rub, turn," with derivatives referring to boring and drilling (see throw (v.)).
Atreus: son of Pelops, father of Agamemnon and Menelaeus.
atria (n.): classical plural of atrium.
atrial (adj.): by 1860 in the medical sense, from atrium + -al (1).
atrium (n.): 1570s, from Latin atrium "central court or main room of an ancient Roman house, room which contains the hearth," sometimes said (on authority of Varro, "De Lingua Latina") to be an Etruscan word, but perhaps from PIE *ater- "fire," on notion of "place where smoke from the hearth escapes" (through a hole in the roof). Anatomical sense of "either of the upper cavities of the heart" first recorded 1870. Meaning "skylit central court in a public building" first attested 1967.
atrocious (adj.): 1660s, from stem of Latin atrox "fierce, savage, cruel" (see atrocity) + -ous. Colloquial sense "very bad" is late 19c. Related: Atrociously; atrociousness.
atrocity (n.): 1530s, from Middle French atrocité or directly from Latin atrocitatem (nominative atrocitas) "cruelty, fierceness, harshness," noun of quality from atrox "fierce, cruel, frightful," from PIE *atro-ek-, from root *ater- "fire" (see atrium) + *okw- "see" (see eye (n.)); thus "of fiery or threatening appearance." The meaning "an atrocious deed" is from 1793.
atrophic (adj.): 1819; see atrophy + -ic.
atrophy (n.): "a wasting away through lack of nourishment," 1620s (atrophied is from 1590s), from French atrophie, from Late Latin atrophia, from Greek atrophia "a wasting away," noun of state from atrophos "ill-fed, un-nourished," from a- "not" + trophe "nourishment," from trephein "to fatten" (see -trophy).
atrophy (v.): 1822 (implied in atrophied), from atrophy (n.). Related: Atrophying.
atropine (n.): 1836, from Latin atropa "deadly nightshade" (from which the alkaloid poison is extracted), from Greek atropos "inflexible," also the name of one of the Fates (see Atropos) + chemical suffix -ine (2).
Atropos: one of the Fates (the one who holds the shears and determines the manner of a person's death and cuts the thread), from Greek, "inflexible," literally "not to be turned away," from a- "not" (see a- (3)) + stem of trepein "to turn" (see trope). Related form Atropa was the Greek name for deadly nightshade.
attaboy: 1909, probably from common pronunciation of "that's the boy!" a cheer of encouragement or approval.
attach (v.): mid-14c. (mid-13c. in Anglo-Latin), "to take or seize (property or goods) by law," a legal term, from Old French atachier (11c.), earlier estachier "to attach, fix; stake up, support" (Modern French attacher, also cf. Italian attaccare), perhaps from a- "to" + Frankish *stakon "a post, stake" or a similar Germanic word (see stake (n.)). Meaning "to fasten, affix, connect" is from c.1400. Related: Attached; attaching.
attachable (adj.): 1570s, from attach + -able.
attache (n.): 1835, from French attaché "junior officer attached to the staff of an ambassador, etc.," literally "attached," past participle of attacher "to attach" (see attach). Attache case "small leather case for carrying papers" first recorded 1900.
attached (adj.): "affectionate, devoted, fond," 1793, past participle adjective from attach.
attachment (n.): c.1400, "arrest of a person on judicial warrant" (mid-13c. in Anglo-Latin), from French attachement, from attacher (see attach). Application to property (including, later, wages) dates from 1590s; meaning "sympathy, devotion" is recorded from 1704; that of "something that is attached to something else" dates from 1797 and has become perhaps the most common use since the rise of e-mail.
attack (v.): c.1600, from French attaquer (16c.), from Florentine Italian attaccare (battaglia) "join (battle)," thus the word is a doublet of attach, which was used 15c.-17c. also in the sense now reserved to attack. Related: Attacked; attacking.
attack (n.): 1660s, from attack (v.). Cf. Middle English attach "a seizure or attack" (of fever), late 14c.
attain (v.): c.1300, "to succeed in reaching," from stem of Old French ataindre (11c., Modern French atteindre) "to come up to, reach, attain, endeavor, strive," from Vulgar Latin *adtangere, from Latin attingere "to touch, to arrive at," from ad- "to" (see ad-) + tangere "to touch" (see tangent). Latin attingere had a wide range of meanings, including "to attack, to strike, to appropriate, to manage," all somehow suggested by the literal sense "to touch." Related: Attained; attaining.
attainable (adj.): 1640s; see attain + -able. Related: Attainability.
attainder (n.): "extinction of rights of a person sentenced to death or outlaw," mid-15c., from noun use of Old French ataindre "to touch upon, strike, hit, seize, accuse, condemn" (see attain). For use of French infinitives as nouns, especially in legal language, cf. waiver.
attainment (n.): late 14c., "encroachment" (a sense now obsolete), from Old French ataignement (Modern French atteignement), from ataindre; see attain. Meaning "action of attaining" is from 1540s; sense of "that which is attained, personal accomplishment" dates from 1670s.
attar (n.): 1798, from Persian 'atar-gul "essence of roses," from 'atar "fragrance," from Arabic 'utur "perfumes, aromas."
attemper (v.): late 14c., from Old French attemprer, from Latin attemperare, from ad- "to" (see ad-) + temperare (see temper (v.)). Related: Attempered; attempering.
attempt (v.): late 14c., from Old French attempter (14c.), earlier atenter "to try, attempt, test," from Latin attemptare "to try" (cf. Italian attentare, Old Provençal, Portuguese attentar, Spanish atentar), from ad- "to, upon" (see ad-) + temptare "to try" (see tempt). Related: Attempted; attempting.
attempt (n.): 1530s, from attempt (v.). Meaning "effort to accomplish something by violence" is from 1580s, especially as an assault on someone's life.
attend (v.): c.1300, "to direct one's mind or energies," from Old French atendre (12c., Modern French attendre) "to expect, wait for, pay attention," and directly from Latin attendere "give heed to," literally "to stretch toward," from ad- "to" (see ad-) + tendere "stretch" (see tenet). The notion is of "stretching" one's mind toward something. Sense of "take care of, wait upon" is from early 14c. Meaning "to pay attention" is early 15c.; that of "to be in attendance" is mid-15c. Related: Attended; attending.
attendance (n.): late 14c., "act of attending to one's duties," from Old French atendance "attention, wait, hope, expectation," from atendant, present participle of atendre (see attend). Meaning "action of waiting on someone" dates from late 14c. (to dance attendance on someone is from 1560s); that of "action of being present, presenting oneself" (originally with intent of taking a part) is from mid-15c. Meaning "number of persons present" is from 1835.
attendant (n.): 1550s, "one who waits upon," from the adjective, or from Middle French atendant, noun use of present participle of atendre (see attend).
attendant (adj.): late 14c., "solicitous, attentive," see attendant (n.). Sense of "serving under, accompanying in a dependant position" is from c.1400.
attendee (n.): "one who attends" (something), 1961, from attend + -ee. Attender is older (mid-15c.) but had senses "one who waits upon" and "one who gives heed."