Online Etymology Dictionary

aperitif (n.): 1894, "alcoholic drink taken before a meal to stimulate the appetite," from French apéritif "laxative, laxative liqueur," literally "opening," from Latin aperitivus, from aperire "to open" (see overt). Compare Middle English apertive (adj.), a medical word meaning "capable of opening or dilating" (pores, etc.), early 15c.
apert (adj.): c. 1300, from Old French apert and directly from Latin apertus "open," past participle of aperire "to open, uncover" (see overt).
aperture (n.): early 15c., from Latin apertura "an opening," from apertus, past participle of aperire "to open" (see overt).
apex (n.): c. 1600, from Latin apex "summit, peak, tip, top, extreme end;" probably related to apere "to fasten, fix," hence "the tip of anything" (one of the meanings in Latin was "small rod at the top of the flamen's cap"), from PIE *ap- "to take, reach." Proper plural is apices.
aphasia (n.): "loss of ability to speak," especially as result of brain injury or disorder, 1867, from Modern Latin aphasia, from Greek aphasia "speechlessness," from a- "without" (see a- (3)) + phasis "utterance," from phanai "to speak," related to pheme "voice, report, rumor" (see fame (n.)).
APHASIA is the term which has recently been given to the loss of the faculty of articulate language, the organs of phonation and of articulation, as well as the intelligence, being unimpaired. The pathology of this affection is at the present time the subject of much discussion in the scientific world; the French Academy devoted several of their séances during the year 1865 to its special elucidation, and the Medical Journals of France and of our own country have lately contained a good deal of original matter bearing upon this obscure feature in cerebral pathology. [Frederic Bateman, M.D., "Aphasia," London, 1868]
aphasic: 1868 (n.); 1892 (adj.), from aphasia + -ic.
aphelion (n.): "point farthest from the sun" (of a celestial body's orbit), 1670s, a Grecianized form of Modern Latin aphelium, altered by Johannes Kepler based on Greek apo heliou "away from the sun," from apo "away from" (see apo-) + heliou, genitive of helios "sun" (see sol). The whole was formed on the model of Ptolemaic apogaeum (see apogee) to reflect the new helio-centric model of the universe.
aphetic (adj.): 1880, from aphesis (1880), coined by OED editor Sir James A.H. Murray (1837-1915) for "gradual and unintentional loss of a short unaccented vowel at the beginning of a word" (as squire from esquire), from Greek aphienai "to let go, to send forth," from apo- "from" (see apo-) + hienai "to send" (see jet (v.)).
aphid (n.): 1884, Englished from Modern Latin aphides, plural of aphis, coined by Linnaeus (1758), though where he got it and why he applied it to the plant louse are mysteries. The theory favored by OED as "least improbable" is that it derives from the plural of Greek apheides "unsparing, lavishly bestowed," in reference either to the "prodigious rate of production" of the insects or their voracity. They also are known as ant-cows.
aphonia (n.): "want of voice, loss of voice, having no sound," 1719, from Modern Latin aphonia, from Greek aphonia "speechlessness," noun of quality from aphonos "voiceless," from a-, privative prefix (see a- (3)), + phone "voice," from PIE root *bha- (2) "to speak, tell, say" (see fame (n.)) + abstract noun ending -ia. Less-common Englished form aphony is attested from 1827.
aphorism (n.): 1520s (especially in reference to the "Aphorisms of Hippocrates"), from Middle French aphorisme (14c., aufforisme), from Late Latin aphorismus, from Greek aphorismos "definition, pithy sentence," from aphorizein "to mark off, divide," from apo- "from" (see apo-) + horizein "to bound" (see horizon).

An aphorism is a short, pithy statement containing a truth of general import; an axiom is a statement of self-evident truth; a theorem is a demonstrable proposition in science or mathematics; an epigram is like an aphorism, but lacking in general import. Maxim and saying can be used as synonyms for aphorism.
aphoristic (adj.): 1753, from Greek aphoristikos (see aphorism). Aphoristically is from 1650s.
aphotic (adj.): "untouched by sunlight, lightless" (in reference to deep-sea regions), 1903, Modern Latin, from Greek a- "not, without" (see a- (3)) + phos (genitive photos) "light," related to phainein "to show, to bring to light" (see phantasm) + -ic. Aphotic zone is recorded from 1913.
Aphra: fem. proper name, apparently from a misunderstanding of Hebrew bebheth 'Aphrah "in the house of Aphrah" (Mi. i:10), in which Aphrah probably is the name of a town, not a person. [Klein]
aphrodisiac (n.): 1719, from Greek aphrodisiakos "inducing sexual desire," from aphrodisios, "pertaining to Aphrodite; sexual pleasure; a temple of Aphrodite," Greek goddess of love and beauty. As an adjective from 1830 (earlier was aphrodisical, 1719)
Aphrodite (n.): Greek goddess of love and beauty; by the ancients, her name was derived from Greek aphros "foam," from the story of her birth, but perhaps it is ultimately from Phoenician Ashtaroth (Assyrian Ishtar). In 17c. English, pronounced to rhyme with night, right, etc.
apiarist (n.): 1816; see apiary + -ist.
apiary (n.): 1650s, from Latin apiarium "beehouse, beehive," neuter of apiarius "of bees," from apis "bee," a mystery word unrelated to any similar words in other Indo-European languages. A borrowing from Semitic has been proposed.
apical (adj.): "of or belonging to an apex," 1828, from Latin apicem, from apex (see apex) + -al (1).
apiece (adv.): 1550s, a contraction of a pece (mid-15c.), originally of coins, objects for sale, etc. (see a (2) + piece (n.)).
aping (n.): "imitation, mimicry," 1680s, verbal noun from ape (v.).
aplasia (n.): 1885, medical Latin, from Greek a-, privative prefix (see a- (3)), + -plasia.
aplenty (adj.): 1830, originally U.S., from a- (1) + plenty (n.). First attested in writings of J. Fenimore Cooper.
aplomb (n.): "assurance, confidence," 1828, from French aplomb (16c.), literally "perpendicularity," from phrase à plomb "poised upright, balanced," literally "on the plumb line," from Latin plumbum "(the metal) lead" (see plumb (n.)), of which the weight at the end of the line was made.
apnea (n.): "suspension of breathing," also apnoea, 1719, Modern Latin, from Greek apnoia "absence of respiration," from apnos "without breathing," from a- "not" (see a- (3)) + pnein "to breathe" (see pneuma).
apneic (adj.): 1883, from apnea + -ic.
apo koinu: Greek, literally "in common." Applied to sentences with one subject and two predicates; a formation rare in modern English, though it occurs more often in Old English. Compare koine.
apo-: before vowels ap-, word-forming element meaning "from, away from, separate, free from," from Greek apo "from, away from; after; in descent from," in compounds, "from, asunder, away, off; finishing, completing; ceasing from; back again," from PIE root *apo- "off, away" (source also of Sanskrit apa "away from," Avestan apa "away from," Latin ab "away from, from," Gothic af, Old English of "away from").
apocalypse (n.): late 14c., "revelation, disclosure," from Church Latin apocalypsis "revelation," from Greek apokalyptein "uncover, disclose, reveal," from apo- "from" (see apo-) + kalyptein "to cover, conceal" (see Calypso). The Christian end-of-the-world story is part of the revelation in John of Patmos' book "Apokalypsis" (a title rendered into English as "Apocalypse" c. 1230 and "Revelations" by Wyclif c. 1380).

Its general sense in Middle English was "insight, vision; hallucination;" meaning "a cataclysmic event" is modern. As agent nouns, apocalypst (1829), apocalypt (1834), and apocalyptist (1835) have been tried.
apocalyptic (adj.): 1660s, "pertaining to the 'Revelation of St. John' in the New Testament," from Greek apokalyptikos, from apokalyptein (see apocalypse). Meaning "pertaining to the imminent end of the world" evolved by 1880s.
Apocrypha: late 14c., neuter plural of Late Latin apocryphus "secret, not approved for public reading," from Greek apokryphos "hidden; obscure," thus "(books) of unknown authorship" (especially those included in the Septuagint and Vulgate but not originally written in Hebrew and not counted as genuine by the Jews), from apo- "away" (see apo-) + kryptein "to hide" (see crypt). Properly plural (the single would be Apocryphon or apocryphum), but commonly treated as a collective singular.
apocryphal (adj.): 1580s, "of doubtful authenticity," from Apocrypha + -al (1). Middle English had apocrive (late 14c.) in same sense.
apodal (adj.): 1769, with -al + Greek apous (genitive apodos) "footless," from a-, privative prefix (see a- (3)) + pous "foot," from PIE root *ped- (1) "a foot" (see foot (n.)).
apodictic (adj.): "clearly demonstrated," 1650s, from Latin apodicticus, from Greek apodeiktikos, from apodeiktos, verbal adjective of apodeiknynai "to show off, demonstrate," literally "to point away from" (other objects, at one), from apo "off, away" (see apo-) + deiknynai "to show" (see diction).
apodyterium (n.): 1690s, from Latin apodyterium "undressing room" (in a bath house), from Greek apodyterion "undressing room," from apodyein "to put off, undress," from apo- "off" (see apo-) + dyein "to put on, enter, go in."
apogee (n.): "point at which the moon is farthest from the earth," 1590s, from French apogée, from Latin apogaeum, from Greek apogaion, neuter adjective, "away from the earth," a term from Ptolemaic astronomy, from apo "off, away" (see apo-) + gaia/ge "earth" (see Gaia). Adjective forms are apogeal, apogean.
apolitical (adj.): 1947, from a- "not" (see a- (3)) + political.
Apollo: Olympian deity, god of music, poetry, medicine, etc., later identified with Helios, the sun god; the name is a Latin form of Greek Apollon, said to be perhaps related to an obsolete Greek verb meaning "to drive away" (evil, etc.) [Klein, citing Usener].
Apollonian (adj.): 1660s, from Apollo (Greek Apollon) + -ian. The Greek adjective was Apollonios. The word also is attested in English as Apollinarian (1753), Apolline (c. 1600).
Apollyon: destroying angel of the bottomless pit (a name sometimes given to the Devil), late 14c., from present participle of Greek apollyein "to destroy utterly" (from apo- "from, away from" + olluein "to destroy"); a translation of Hebrew Abaddon (q.v.).
apologetic (adj.): 1640s, "vindicatory," from French apologétique, from Latin apologeticus, from Greek apologetikos "defensible," from apologeisthai (see apology). Meaning "regretfully acknowledging failure" is from 1855. As a noun, "formal defense," from early 15c. Related: Apologetics (c. 1753).
apologia (n.): see apology.
apological (adj.): c. 1600; see apology + -ical.
apologise (v.): chiefly British English spelling of apologize; for suffix, see -ize. Related: Apologised; apologising.
apologist (n.): 1630s, from French apologiste, from apologie (see apology).
apologize (v.): 1590s, "to speak in defense of;" see apology + -ize. Main modern sense "to regretfully acknowledge" is attested by 1725. The Greek equivalent, apologizesthai, meant simply "to give an account." Related: Apologized; apologizing.
apologue (n.): "moral fable," 1550s, from French apologue, from Latin apologus, from Greek apologos, from apo- "off, away from" (see apo-) + logos "speech" (see lecture (n.)). Literally, "(that which comes) from a speech."
apology (n.): early 15c., "defense, justification," from Late Latin apologia, from Greek apologia "a speech in defense," from apologeisthai "to speak in one's defense," from apologos "an account, story," from apo- "from, off" (see apo-) + logos "speech" (see lecture (n.)).

The original English sense of "self-justification" yielded a meaning "frank expression of regret for wrong done," first recorded 1590s, but this was not the main sense until 18c. The old sense tends to emerge in Latin form apologia (first attested in English 1784), especially since J.H. Newman's "Apologia pro Vita Sua" (1864).
aponeurosis (n.): 1670s, from Latin, from Greek aponeurosis, from aponeuroein, from apo- "off, away from" (see apo-) + neuron "sinew" (see neuro-).
apophatic (adj.): "involving a mention of something one feigns to deny; involving knowledge obtained by negation," 1850, from Greek apophatikos, from apophasis "denial, answer," from apophanai "to speak off," from apo- "off" (see apo-) + phanai "to speak," related to pheme "voice," from PIE root *bha- (2) "to speak, tell, say" (see fame (n.)).