Online Etymology Dictionary

apophthegm (n.): see apothegm.
apoplectic (adj.): 1610s, "involving apoplexy," from French apoplectique (16c.), from Latin apoplecticus, from Greek apoplektikos "disabled by a stroke, crippled, struck dumb," from apoplektos, verbal adjective of apoplessein (see apoplexy). Meaning "showing symptoms of apoplexy" (1721) gradually shaded into "enraged, very angry."
apoplexy (n.): late 14c., "sudden fit of paralysis and dizziness," from Old French apoplexie or directly from Late Latin apoplexia, from Greek apoplexia, from apoplessein "to strike down and incapacitate," from apo- "off" (see apo-), in this case probably an intensive prefix, + plessein "to hit" (compare plague (n.), also with a root sense of "stricken"). The Latin translation, sideratio, means "disease caused by a constellation."
aporetic (adj.): c. 1600, from French aporetique, from Greek aporetikos, from aporeein "to be at a loss," from aporos "impassable, impracticable, very difficult; hard to deal with; at a loss," from a-, privative prefix (see a- (3)), + poros "passage" (see pore (n.)).
aporia (n.): 1580s, from Latin, from Greek aporia, noun of state from aporos (see aporetic).
aposiopesis (n.): rhetorical artifice wherein the speaker suddenly breaks off in the middle of a sentence, 1570s, from Latin, from Greek aposiopesis "a becoming silent," also as a rhetorical figure, from apo- (see apo-) + siope "silence."
apostasy (n.): late 14c., "renunciation, abandonment or neglect of established religion," from Latin apostasia, from later Greek apostasia, from apostasis "revolt, defection," literally "a standing off" (see apostate). General (non-religious) sense is attested from 1570s.
apostate (n.): mid-14c., "one who forsakes his religion or faith," from Old French apostate (Modern French apostat) and directly from Late Latin apostata, from Greek apostasia "defection, desertion, rebellion," from apostenai "to defect," literally "to stand off," from apo- "away from" (see apo-) + stenai "to stand." Used in non-religious situations (politics, etc.) from mid-14c.
apostate (adj.): late 14c.; see apostate (n.).
apostatize (v.): 1610s, from Late Latin apostatizare, earlier apostatare, from apostata (see apostate). Related: Apostatized; apostatizing. The past participle form apostazied is attested from late 14c.
apostille (n.): "note, especially on text of the Bible," also apostil, 1520s, from French apostille (15c.), probably from Medieval Latin postilla, which probably represents Latin post illa, literally "after those."
apostle (n.): Old English apostol "messenger," especially the 12 witnesses sent forth by Jesus to preach his Gospel, from Late Latin apostolus, from Greek apostolos "messenger, person sent forth," from apostellein "send away, send forth," from apo- "from" (see apo-) + stellein in its secondary sense of "to send," from PIE *stel-yo-, suffixed form of root *stel- "to put, stand," with derivatives referring to a standing object or place (see stall (n.1)). Compare epistle.

The current form of the word, predominant since 16c., is influenced by Old French apostle (12c.), from the same Late Latin source. Figurative sense of "chief advocate of a new principle or system" is from 1810. Apostles, short for "The Acts and Epistles of the Apostles," is attested from c. 1400.
apostolic (adj.): early 15c., from French apostolique or directly from Church Latin apostolicus, from Greek apostolikos, from apostolos (see apostle). Apostolical also is early 15c.
apostrophe (n.): mark indicating omitted letter, 1580s, from Middle French apostrophe, from Late Latin apostrophus, from Greek apostrophos (prosoidia) "(the accent of) turning away," thus, a mark showing where a letter has been omitted, from apostrephein "avert, turn away," from apo- "from" (see apo-) + strephein "to turn" (see strophe).

In English, the mark often represents loss of -e- in -es, possessive ending. It was being extended to all possessives, whether they ever had an -e- or not, by 18c. Greek also used this word for a "turning aside" of an orator in speech to address some individual, a sense first recorded in English 1530s.
apothecary (n.): mid-14c., "shopkeeper, especially one who stores, compounds, and sells medicaments," from Old French apotecaire (13c., Modern French apothicaire), from Late Latin apothecarius "storekeeper," from Latin apotheca "storehouse," from Greek apotheke "barn, storehouse," literally "a place where things are put away," from apo- "away" (see apo-) + tithenai "to put, to place" (see theme). Same root produced French boutique and Spanish bodega. Cognate compounds produced Sanskrit apadha- "concealment," Old Persian apadana- "palace."

Drugs and herbs being among the chief items of non-perishable goods, the meaning narrowed 17c. to "druggist" (Apothecaries' Company of London separated from the Grocers' in 1617). Apothecaries formerly were notorious for "the assumed gravity and affectation of knowledge generally put on by the gentlemen of this profession, who are commonly as superficial in their learning as they are pedantic in their language" [Francis Grose, "A Classical Dictionary of the Vulgar Tongue," 1796]. Hence, Apothecary's Latin, barbarously mangled, also known as Dog Latin.
apothegm (n.): "pithy saying," 1550s, from Greek apophthegma "terse, pointed saying," literally "something clearly spoken," from apophthengesthai "to speak one's opinion plainly," from apo- "from" (see apo-) + phthengesthai "to utter." See aphorism for nuances of usage. Spelling apophthegm, restored by Johnson, is preferred in England, according to OED.
apotheosis (n.): 1600s, from Late Latin apotheosis "deification," from Greek apotheosis, from apotheoun "deify, make (someone) a god," from apo- special use of this prefix, meaning, here, "change" + theos "god" (see theo-).
apotheosize (v.): 1760; see apotheosis + -ize. Related: Apotheosized; apotheosizing. Earlier in same sense was apotheose (1670s).
apothesis (n.): 1811, from Greek apothesis "a laying up in store; a putting aside," noun of action from apotithenai "to lay aside," from apo- "off, away" (see apo-) + tithenai "to put, place" (see theme).
apotropaic (adj.): 1883, with -ic + Greek apotropaios "averting evil," from apotrepein "to turn away, avert," from apo- "off, away" (see apo-) + trepein "to turn" (see trope).
app (n.): computerese shorthand for application, attested by 1992.
Appalachia: "cultural and geographical region of inland Eastern U.S.," 1880s, from the Appalachian Mountains, which are its core. Earlier Appalachia was proposed as a better name for "United States of America" by Washington Irving in 1839 (though he preferred Alleghenia) and this may have been the coinage of the word.
It is a thousand pities that the puny witticisms of a few professional objectors should have the power to prevent, even for a year, the adoption of a name for our country. At present we have, clearly, none. There should be no hesitation about "Appalachia." In the first place, it is distinctive. "America" is not, and can never be made so. We may legislate as much as we please, and assume for our country whatever name we think right — but to use it will be no name, to any purpose for which a name is needed, unless we can take it away from the regions which employ it at present. South America is "America," and will insist upon remaining so. [Edgar Allan Poe, 1846]
Appalachian: in reference to the North American mountain range, c. 1600, Mountaynes Apalatsi; written apalachen by Spanish explorers and originally in reference only to the southern end of the range. Originally the name of the Apalachee, a Muskogean people of northwestern Florida, perhaps from Apalachee abalahci "other side of the river" or Hitchiti (Muskogean) apalwahči "dwelling on one side." Spelling shifted under influence of adjectives in -ian.
appall (v.): also appal, early 14c., "to fade;" c. 1400, "to grow pale," from Old French apalir "become or make pale," from a- "to" (see ad-) + palir "grow pale," from Latin pallere (see pallor). Meaning "cause dismay or shock," is 1530s. Related: Appalled; appalling.
appalled (adj.): 1570s, "enfeebled;" c. 1600, "dismayed;" past participle adjective from appall.
appalling (adj.): 1620s, present participle adjective from appall. Colloquial weakened sense of "distasteful" is attested from 1919.
Appaloosa: breed of horses favored by Indian tribes in U.S. West, 1849, either from Opelousa in Louisiana or from Palouse Indians, who lived near the river of that name in Idaho, in which case it probably is a Nez Percé word. Opelousa is perhaps from Choctaw api losa "black body;" while Palouse is from Sahaptin palou:s "what is standing up in the water."
appanage (n.): c. 1600, from French apanage (13c.), from apaner "to endow with means of subsistence," from Medieval Latin appanare "equip with bread," from ad- "to" (see ad-) + panis "bread," from PIE root *pa- "to feed" (see food). Originally, provisions made for younger children of royalty. The double -p- restored in French 15c.-16c., in English 17c.
apparat (n.): "administrative machinery of the Communist Party in Russia," 1950, from Russian, from German apparat "apparatus, instrument," from Latin apparatus (see apparatus).
apparatchik (n.): "Communist agent or spy," 1941, originally in writings of Arthur Koestler, from Russian, from apparat "political organization" (see apparat). Russian plural is apparatchiki.
apparatus (n.): 1620s, from Latin apparatus "tools, implements, equipment; preparation, a preparing," noun of state from past participle stem of apparare "prepare," from ad- "to" (see ad-) + parare "make ready" (see pare).
apparel (v.): mid-13c., "to equip (in any way)," from Old French apareillier (12c.), from Vulgar Latin *appariculare. This is either from Latin apparare "prepare, make ready" (see apparatus), or from Vulgar Latin *ad-particulare "to put things together." The meaning "to attire in proper clothing" is from mid-14c. Cognate with Italian aparecchiare, Spanish aparejar, Portuguese aparelhar. Related: Appareled; apparelled; appareling; apparelling.
apparel (n.): "personal outfit or attire," early 14c., also "ship's rigging," from Old French apareil "preparation," from apareillier (see apparel (v.)). Earlier in same sense was apparelment (early 14c.).
apparent (adj.): late 14c., from Old French aparant "evident, obvious, visible," from Latin apparentem (nominative apparens) "visible, manifest," present participle of apparere (see appear). First attested in phrase heir apparent (see heir). Meaning "superficial" is c. 1400. Apparent magnitude in astronomy (how bright a heavenly body looks from earth, as opposed to absolute magnitude, which is how bright it really is) is attested from 1875.
apparently (adv.): late 14c., "visibly, openly," from apparent + -ly (2). Meaning "evidently" is from 1550s; that of "to all appearances" (but not necessarily "really") is from 1560s; meaning "so far as can be judged, seemingly," is from 1846. A gradual retreat from certainty.
apparition (n.): c. 1500, "unclosing" (of Heaven), from Anglo-French aparicion, Old French apparition, aparoison (15c.), used in reference to the Epiphany (revealing of Christ child to the Wise Men), from Late Latin apparitionem (nominative apparitio) "an appearance," also "attendants," in classical Latin "service, servants," noun of action from past participle stem of apparere "appear" (see appear). Meaning "ghost" first recorded c. 1600; the shade of sense differentiation between appearance and apparition is that the latter tends to be unexpected or startling.
appeal (v.): early 14c., originally in legal sense of "to call" to a higher judge or court, from Anglo-French apeler "to call upon, accuse," Old French apeler "make an appeal" (11c., Modern French appeler), from Latin appellare "to accost, address, appeal to, summon, name," iterative of appellere "to prepare," from ad- "to" (see ad-) + pellere "to beat, drive" (see pulse (n.1)). Related: Appealed; appealing.

Probably a Roman metaphoric extension of a nautical term for "driving a ship toward a particular landing." Popular modern meaning "to be attractive or pleasing" is quite recent, attested from 1907 (appealing in this sense is from 1891), from the notion of "to address oneself in expectation of a sympathetic response."
appeal (n.): c. 1300, in the legal sense, from Old French apel (Modern French appel), back-formation from apeler (see appeal (v.)). Meaning "call to an authority" is from 1620s; that of "attractive power" attested by 1916.
appealing: mid-15c. as a noun, "action of petitioning a higher court or authority," verbal noun from appeal (v.). Adjectival sense of "attractive" attested by 1892. Related: Appealingly.
appear (v.): late 13c., "to come into view," from stem of Old French aparoir (12c., Modern French apparoir) "appear, come to light, come forth," from Latin apparere "to appear, come in sight, make an appearance," from ad- "to" (see ad-) + parere "to come forth, be visible." Of persons, "present oneself," late 14c. Meaning "seem, have a certain appearance" is late 14c. Related: Appeared; appearing.
appearance (n.): late 14c., "visible state or form, figure; mere show," from Anglo-French apparaunce, Old French aparance "appearance, display, pomp" (13c.), from Latin apparentia, abstract noun from aparentem, past participle of apparere (see appear). Meaning "semblance" is recorded from early 15c.; that of "action of coming into view" is mid-15c. Phrase keep up appearances attested from 1760 (save appearances in same sense is 1711).
appeasable (adj.): 1540s; see appease + -able. Related: Appeasably.
appease (v.): c. 1300 "to reconcile," from Anglo-French apeser, Old French apaisier "to pacify, make peace, appease, be reconciled, placate" (12c.), from the phrase a paisier "bring to peace," from a "to" (see ad-) + pais, from Latin pacem (nominative pax) "peace" (see peace). Related: Appeased; appeasing.
appeasement (n.): mid-15c., "pacification," from Middle French apeisement, Old French apaisement "appeasement, calming," noun of action from apaisier (see appease). First recorded 1919 in international political sense; not pejorative until failure of Chamberlain's policy toward Germany in 1939 (Methods of appeasement was Chamberlain's description of his policy).
appeaser (n.): mid-15c., agent noun from appease (v.). Political sense attested from 1940.
appellant (n.): late 14c., Anglo-French, from Old French apelant, noun use of present participle of apeler, from Latin appellare (see appeal).
appellate (adj.): "pertaining to appeals," 1726, from Latin appellatus, past participle of appellare (see appeal). Appellate jurisdiction is in Blackstone (1768).
appellation (n.): late 15c., "action of appealing" (to a higher authority), from Old French apelacion (13c.), from Latin appellationem (nominative appellatio) "an addressing, accosting; an appeal; a name, title," noun of action from past participle stem of appellare (see appeal). Meaning "designation, name given to a person, thing, or class" is from mid-15c., from a sense also found in Middle French appeler.
appellative (adj.): mid-15c., from Latin appellativus, from appellat-, past participle stem of appellare (see appeal (v.)). As a noun, attested from 1590s.
appellee (n.): 1530s, from Anglo-French (late 14c.), from Old French apelé (Modern French appelé) "accused, defendant," noun use of past participle of appeler "to call, address;" see appeal + -ee.