Online Etymology Dictionary

apprehensible (adj.): late 15c., from Latin apprehensibilis "that can be seized," from apprehens-, past participle stem of apprehendere (see apprehend).
apprehension (n.): "perception, comprehension," late 14c., from Old French apprehension or directly from Latin apprehensionem (nominative apprehensio), noun of action from past participle stem of apprehendere (see apprehend). Sense of "seizure on behalf of authority" is 1570s; that of "anticipation" (usually with dread) is recorded from c. 1600.
apprehensive (adj.): late 14c., "capable of perceiving, fitted for mental impression," from Medieval Latin apprehensivus, from Latin apprehensus, past participle of apprehendere (see apprehend). Meaning "fearful of what is to come" is recorded from 1718, via notion of "capable of grasping with the mind" (c. 1600). Related: Apprehensively; apprehensiveness.
apprentice (n.): c. 1300, from Old French aprentiz "someone learning" (13c., Modern French apprenti, taking the older form as a plural), also as an adjective, "unskilled, inexperienced," from aprendre (Modern French apprendre) "to learn; to teach," contracted from Latin apprehendere (see apprehend). Shortened form prentice long was more usual in English.
apprentice (v.): 1630s, from apprentice (n.). Related: Apprenticed; apprenticing.
apprenticeship (n.): 1590s, from apprentice (n.) + -ship. Replaced earlier apprenticehood (late 14c., with -hood).
apprise (v.): "to notify," 1690s, from French appris, past participle of apprendre "to inform, teach," literally "to lay hold of (in the mind)," another metaphoric meaning of Latin apprehendere (see apprehend). Related: Apprised; apprising.
apprize (v.): occasional legalese form of appraise, c. 1400. Related: Apprized; apprizing.
approach (v.): c. 1300, from Anglo-French approcher, Old French aprochier "approach, come closer" (12c., Modern French approcher), from Late Latin appropiare "go nearer to," from Latin ad- "to" (see ad-) + Late Latin propiare "come nearer," comparative of Latin prope "near" (see propinquity). Replaced Old English neahlæcan.
approach (n.): mid-15c., from approach (v.). Figurative sense of "means of handling a problem, etc." is first attested 1905.
approachable (adj.): 1570s, from approach (v.) + -able. Figurative sense, "affable, friendly," is from 1610s. Related: Approachably; approachability.
approbate (v.): late 15c., from Latin approbatus, past participle of approbare "to assent to (as good), favor" (see approve). Related: Approbated; approbating.
approbation (n.): late 14c., "proven effectiveness, excellence," from Old French aprobacion or directly from Latin approbationem (nominative approbatio) "an approval," noun of action from past participle stem of approbare (see approve). Meaning "approval, endorsement" is from early 15c.
appropre (v.): mid-14c., from Old French aproprier, from Late Latin appropriare (see appropriate (v.)).
appropriate (v.): early 15c., "take possession of," from Late Latin appropriatus, past participle of appropriare, adpropriare (c.450) "to make one's own," from Latin ad- "to" (see ad-) + propriare "take as one's own," from proprius "one's own" (see proper). Related: Appropriated; appropriating.
appropriate (adj.): "specially suitable, proper," early 15c., from Latin appropriatus, past participle of appropriare (see appropriate (v.)). Related: Appropriately; appropriateness.
appropriation (n.): late 14c., "taking (something) as private property," from Late Latin appropriationem (nominative appropriatio) "a making one's own," noun of action from past participle stem of appropriare (see appropriate). Meaning "setting aside for some purpose" (especially of money) first attested 1789 in U.S. Constitution.
approval (n.): 1680s, from approve + -al (2). According to OED, "Rare bef. 1800; now generally used instead of" approvance (1590s, from French aprovance).
approve (v.): c. 1300, "to demonstrate, prove;" mid-14c., "to attest (something) with authority," from Old French aprover (Modern French approuver) "approve, agree to," from Latin approbare "to assent to as good, regard as good," from ad- "to" (see ad-) + probare "to try, test something (to find if it is good)," from probus "honest, genuine" (see prove).

The meaning extended late 14c. to "to sanction, endorse, confirm formally" then to "assent to (something) as good" (early 15c.), especially in reference to the actions of authorities, parliaments, etc. Related: Approved; approving.
approximate (adj.): early 15c., from Latin approximatus, past participle of approximare "to come near to," from ad- "to" (see ad-) + proximare "come near," from proximus "nearest," superlative of prope "near" (see propinquity).
approximate (v.): early 15c., "to bring or put close," from approximate (adj.). Meaning "to come close" is from 1789. Related: Approximated; approximating.
approximately (adv.): 1742, from approximate (adj.) + -ly (2).
approximation (n.): early 15c., "act of coming near or close," noun of action from approximate (v.). Meaning "result of approximating" is from 1650s.
appurtenance (n.): c. 1300, "right, privilege or possession subsidiary to a principal one," from Anglo-French apurtenance (12c.), Old French apartenance, present participle of apartenir "be related to," from Latin appertinere "to pertain to," from ad- "to" (see ad-) + pertinere "belong to" (see pertain).
appurtenances (n.): "apparatus, gear," late 14c.; see appurtenance.
appurtenant (adj.): late 14c., from Anglo-French apurtenant, Old French apartenant, present participle of apartenir "be related to" (see appurtenance).
apraxia (n.): 1877, medical Latin, from German apraxie (H. Steinthal, 1871), from Greek apraxia "inaction," from privative prefix a- (see a- (3)) + praxis "a doing, action, business" (see praxis) + abstract noun ending -ia.
apricate (v.): 1690s, "to bask in the sun," from Latin apricatus, past participle of apricari "to bask in the sun," from apricus "exposed" (to the sun); perhaps contracted from *apericus, from aperire "to open" (see overt). Transitive sense is recorded from 1851.
apricot (n.): 1550s, abrecock, from Catalan abercoc, related to Portuguese albricoque, from Arabic al-birquq, through Byzantine Greek berikokkia from Latin (malum) praecoquum "early-ripening (fruit)" (see precocious). Form assimilated to French abricot.
Latin praecoquis early-ripe, can probably be attributed to the fact that the fruit was considered a variety of peach that ripened sooner than other peaches .... [Barnhart]
The older Latin name for it was prunum Armeniacum or malum Armeniacum, in reference to supposed origin in Armenia. As a color name, first attested 1906.
April: fourth month, c. 1300, aueril, from Old French avril (11c.), from Latin (mensis) Aprilis, second month of the ancient Roman calendar, of uncertain origin, perhaps based on Apru, an Etruscan borrowing of Greek Aphrodite. Or perhaps *ap(e)rilis "the following, the next," from its place as the second month of the old Roman calendar, from Proto-Italic *ap(e)ro-, from PIE *apo- "away, off" (see apo-; compare Sanskrit aparah "second," Gothic afar "after"). With month-name suffix -ilis as in Quintilis, Sextilis (the old names of July and August). In English in Latin form from mid-12c. Replaced Old English Eastermonað, which was named for a fertility goddess (see Easter). Re-spelled in Middle English on Latin model (apprile first attested late 14c.).
April fool (n.): 1680s; April-gowk (from Old Norse gaukr "a cuckoo") is a northern variant. April Fool's Day customs of sending people on false errands seem to have come to England from France late 17c.; originally All Fool's Day (1712). In Cumberland, Westmorland and northern parts of Lancashire and Yorkshire, however, May 1 was the day for hoaxing, and the fool was a May gosling. That custom was first attested 1791.
apron (n.): mid-15c., faulty separation (as also in adder, umpire) of a napron (c. 1300), from Old French naperon "small table-cloth," diminutive of nappe "cloth," from Latin mappa "napkin." Napron was still in use as recently as late 16c. The shift of Latin -m- to -n- was a tendency in Old French (conter from computare, printemps from primum, natte "mat, matting," from matta). Symbolic of "wife's business" from 1610s. Apron-string tenure was in reference to property held in virtue of one's wife, or during her lifetime only.
Even at his age, he ought not to be always tied to his mother's apron string. [Anne Brontë, "The Tenant of Wildfell Hall," 1848]
apropos (adv.): 1660s, "opportunely," from French à propos "to the purpose," from propos "thing said in conversation, talk; purpose, plan," from Latin propositium "purpose," past participle of proponere "to set forth, propose" (see propound). Meaning "as regards" is 1761, from French. As an adjective, "to the point or purpose," from 1690s.
apse (n.): "semicircular extension at the end of a church," 1846, from Latin apsis "an arch, a vault," from Greek hapsis (Ionic apsis) "loop, arch," originally "a fastening, felloe of a wheel," from haptein "fasten together," which is of unknown origin. The original sense in Greek seems to have been the joining of the arcs to form a circle, especially in making a wheel. The architectural term is earlier attested in English in the Latin form (1706).
apsis (n.): "perigree of the moon, perihelion of a planet" (plural apsides), 1650s, from Latin apsis "arch, vault" (see apse).
apt (adj.): mid-14c., "inclined, disposed;" late 14c., "suited, fitted, adapted," from Old French ate (13c., Modern French apte), or directly from Latin aptus "fit, suited," adjectival use of past participle of *apere "to attach, join, tie to," from PIE root *ap- (1) "to grasp, take, reach" (source also of Sanskrit apnoti "he reaches," Latin apisci "to reach after, attain," Hittite epmi "I seize"). Elliptical sense of "becoming, appropriate" is from 1560s.
aptitude (n.): early 15c., "tendency, likelihood," from Middle French aptitude (14c.) or directly from Late Latin aptitudo (genitive aptitudinis) "fitness," noun of quality from Latin aptus "joined, fitted" (see apt). Meaning "natural capacity to learn" is 1540s; that of "quality of being fit (for a purpose or position)" is from 1640s.
aptly (adv.): early 15c., "by natural means," from apt + -ly (2).
aptness (n.): 1530s, from apt + -ness.
aqua (n.): "water," late 14c.; see aqua-. Used in late Middle English in combinations to mean "decoction, solution" (as in aqua regia, a mix of concentrated acids, literally "royal water," so called for its power to dissolve gold and other "noble" metals). As the name of a light greenish-blue color, 1936.
aqua fortis (n.): old name for "concentrated nitric acid," c. 1600, Latin, literally "strong water;" see aqua- + fort. So called for its power of dissolving metals (copper, silver) unaffected by other agents.
aqua vitae (n.): early 15c., Latin, literally "water of life," an alchemical term for unrefined alcohol. Applied to brandy, whiskey, etc. from 1540s. Compare whiskey, also French eau-de-vie "spirits, brandy," literally "water of life."
aqua-: word-forming element meaning "water," from Latin aqua "water; the sea; rain," cognate with Proto-Germanic *akhwo, source of Old English ea "river," Gothic ahua "river, waters," Old Norse Ægir, name of the sea-god, Old English ieg "island;" all from PIE *akwa- "water" (source also of Sanskrit ap "water," Hittite akwanzi "they drink," Lithuanian uppe "a river").
aquacade (n.): "aquatic entertainment," 1937, American English, from aqua- + -cade, from cavalcade (q.v.).
aquaculture (n.): 1869, from aqua- + culture (n.).
aqualung (n.): 1950, from aqua- + lung. Developed 1943 by Jacques Cousteau and Emile Gagnan.
aquamarine (n.): 1590s, agmarine, "bluish-green type of beryl," from French or Provençal, from Latin aqua marina "sea water," from aqua "water" (see aqua-) + marina, fem. of marinus "of the sea" (see marine (adj.)). Apparently first used as a description of a bluish-green color by John Ruskin, 1846. Abbreviation aqua is attested from 1936.
aquanaut (n.): 1881, from aqua- + ending from Greek nautes "sailor" (see naval).
aquarelle (n.): 1855, from French aquarelle (18c.), from Italian acquerella "water-color," diminutive of acqua, from Latin aqua "water" (see aqua-).
Aquarian (adj.): 1940, in the astrological/New Age sense; see Aquarius + -ian.