Online Etymology Dictionary

accompaniment (n.): 1744, from French accompagnement (13c.), from accompagner (see accompany). Musical sense is earliest.
accompanist (n.): "performer who takes the accompanying part in music," 1833, from accompany + -ist. Fowler prefers accompanyist.
accompany (v.): early 15c., "to be in company with," from Middle French accompagner, from Old French acompaignier (12c.) "take as a companion," from à "to" (see ad-) + compaignier, from compaign (see companion). Related: Accompanied; accompanying.
accomplice (n.): 1580s (earlier complice, late 15c.), from Old French complice "a confederate," from Late Latin complicem (nominative complex) "partner, confederate," from Latin complicare "fold together" (see complicate). With parasitic a- on model of accomplish, etc., or perhaps by assimilation of indefinite article in phrase a complice.
accomplish (v.): late 14c., from Old French acompliss-, present participle stem of acomplir "to fulfill, fill up, complete" (12c.), from Vulgar Latin *accomplere, from Latin ad- "to" (see ad-) + complere "fill up" (see complete (adj.)). Related: Accomplished; accomplishing.
accomplished (adj.): late 15c., "perfect as a result of training," past participle adjective from accomplish (v.). Meaning "completed" is from late 14c.
accomplishment (n.): early 15c., "performance of a task; state of completion," from Old French acomplissement "action of accomplishing," from acomplir (see accomplish). Meaning "thing completed" and that of "something that completes" someone and fits him or her for society are from c. 1600.
accord (v.): early 12c., from Old French acorder (12c.) "reconcile, agree, be in harmony," from Vulgar Latin *accordare "make agree," literally "be of one heart, bring heart to heart," from Latin ad- "to" (see ad-) + cor (genitive cordis) "heart," from PIE root *kerd- (1) "heart" (see heart (n.)). Related: Accorded; according.
accord (n.): late 13c., accourd, from Old French acord "agreement," a back-formation from acorder (see accord (v.)).
accordance (n.): c. 1300, "compliance;" early 14c., "agreement, concurrence," from Old French acordance "agreeing, reconciliation, harmony," noun of action from acorder (see accord). Of things, "conformity, compatibility, harmony," late 14c. Phrase in accordance with is attested from c. 1810 (in Middle English, in accordance of was the usual form).
according: c. 1300, "matching, similar, correponding," present participle adjective and adverb from accord (v.). Meanings "conforming (to), compliant, in agreement; consistent, harmonious; suitable, appropriate" are from late 14c. According to "referring to," literally "in a manner agreeing with" is attested from mid-15c.
accordingly (adv.): mid-14c., "in agreement with," from according + -ly (2). From mid-15c. as "properly; adequately;" meaning "in agreement with logic or expectation" is recorded 1680s.
accordion (n.): 1831, from German Akkordion, from Akkord "musical chord, concord of sounds, be in tune" (compare Italian accordare "to attune an instrument"); ultimately from same source as English accord (v.), with suffix on analogy of clarion, etc. Invented 1829 by piano-maker Cyrill Demian (1772-1847) of Vienna.
accost (v.): 1570s, from Middle French accoster "move up to," from Italian accostare or directly from Late Latin accostare "come up to the side," from Latin ad- "to" (see ad-) + costa "rib, side" (see coast (n.)). The original notion is of fleets of warships attacking an enemy's coast. Related: Accosted; accosting.
accouchement (n.): 1803, from French accouchement, noun of action from accoucher (see accoucheur).
accoucheur (n.): 1759, "midwife" (properly, "male midwife"), from French accoucheur (Jules Clément, later 17c.), agent noun from accoucher "to go to childbed, be delivered" (13c.) originally simply "to lie down" (12c.), from Old French culcher "to lie," from Latin collocare, from com- "with" (see com-) + locare "to place" (see locate). The fem. is accoucheuse (1847).
account (n.): c. 1300, "reckoning of money received and paid," from Old French acont "account, reckoning, terminal payment," from a "to" (see ad-) + cont "counting, reckoning of money to be paid," from Late Latin computus "a calculation," from Latin computare "calculate" (see compute).

Meaning "sum of (one's) money in a bank" is from 1833. Sense of "narration" is first attested 1610s. Plural accounts used as a collective or singular in phrases such as to give accounts (of something), is from mid-13c. Phrase by all accounts is attested from 1798.
account (v.): c. 1300, "to count, enumerate," from Old French aconter "to count, render account" (Modern French conter), from a "to" (see ad-) + conter "to count, tell" (see count (v.)). Meaning "to reckon for money given or received, render a reckoning," is from late 14c.; sense of "to explain" (c. 1710) is from notion of "answer for money held in trust." Transferred sense of "value" is from late 14c. Related: Accounted; accounting.
accountability (n.): 1770, from accountable + -ity. Earlier was accountableness (1660s).
accountable (adj.): "answerable," literally "liable to be called to account," c. 1400 (mid-14c. in Anglo-French); see account (v.) + -able. Related: Accountably.
accountancy (n.): 1854, from accountant + -cy.
accountant (n.): mid-15c., "accounting officer, one who renders accounts," from Old French acuntant (Modern French accomptant), from present participle of accompter (see account (v.)). Sense of "professional maker of accounts" is recorded from 1530s. The word also was an adjective in Middle English, "accountable; liable to render accounts" (early 15c.).
accounting (n.): "reckoning of numbers," late 14c., verbal noun from account (v.). Phrase no accounting for tastes (1823) translates Latin de gustibus non est disputandum.
accouter (v.): also accoutre, 1590s, from French acoutrer, earlier acostrer (13c.) "arrange, dispose, put on (clothing)," originally "sew up," from Vulgar Latin accosturare "to sew together, sew up," from Latin ad- "to" (see ad-) + *consutura "a sewing together," from Latin consutus, past participle of consuere "to sew together," from con- (see com-) + suere "to sew" (see suture). Related: Accoutered; accoutred; accoutering; accoutring.
accoutrements (n.): 1540s, from Middle French accoustrement (Modern French accoutrement), from accoustrer probably from Old French acostrer "arrange," originally "sew up" (see accouter)
accredit (v.): 1610s, from French accréditer, from à "to" (see ad-) + créditer "to credit" (someone with a sum), from crédit "credit" (see credit (n.)). Related: Accredited; accrediting.
accreditation (n.): 1806, noun of action from accredit.
accredited (adj.): "furnished with credentials," 1630s, past participle adjective from accredit (v.).
accretion (n.): 1610s, from Latin accretionem (nominative accretio) "an increasing, a growing larger" (as of the waxing moon), noun of action from past participle stem of accrescere, from ad- "to" (see ad-) + crescere "grow" (see crescent).
accrual (n.): 1782, from accrue + -al (2).
accrue (v.): mid-15c., from Old French acreue "growth, increase, what has grown," fem. of acreu, past participle of acreistre (Modern French accroître) "to increase," from Latin accrescere (see accretion). Related: Accrued; accruing. Apparently a verb from a French noun because there is no English verb to go with it until much later, unless the record is defective.
acculturate (v.): 1934, back-formation from acculturation. Related: Acculturated; acculturating.
acculturation (n.): "the adoption and assimilation of an alien culture," 1880, from ad- "to" + culture (n.) + -ation.
accumulate (v.): 1520s, from Latin accumulatus, past participle of accumulare "to heap up" (see accumulation). Related: Accumulated; accumulating.
accumulated (adj.): past participle adjective from accumulate (v.). It drove out accumulate (adj.) in this sense (except in poetic use) by c. 1700.
accumulation (n.): late 15c., from Latin accumulationem (nominative accumulatio) "a heaping up," noun of action from past participle stem of accumulare "to heap up, amass," from ad- "in addition" (see ad-) + cumulare "heap up," from cumulus "heap" (see cumulus).
accuracy (n.): 1660s, from accurate + -cy.
accurate (adj.): 1610s, "done with care," from Latin accuratus "prepared with care, exact, elaborate," past participle of accurare "take care of," from ad- "to" (see ad-) + curare "take care of" (see cure (n.1)). The notion of doing something carefully led to that of being exact (1650s). Related: Accurately; accurateness.
accursed (adj.): also accurst, early 13c., acursede "lying under a curse," past participle adjective from obsolete verb acursen "pronounce a curse upon, excommunicate" (late 12c.), from a- intensive prefix + cursein (see curse (v.)). The extra -c- is 15c., mistaken Latinism. Weakened sense of "worthy of a curse" is from 1590s. Related: Accursedly; accursedness.
accusation (n.): late 14c., from Old French acusacion or directly from Latin accusationem (nominative accusatio), noun of action from past participle stem of accusare (see accuse).
accusative (n.): grammatical case whose primary function is to express destination or goal of motion, mid-15c., from Anglo-French accusatif, Old French acusatif, or directly from Latin (casus) accusativus "(case) of accusing," from accusatus, past participle of accusare (see accuse).

Translating Greek ptosis aitiatike "case of that which is caused," on similarity of Greek aitiasthai "accuse." Greek aitia is the root of both, and means both "cause" and "accusation," hence the confusion of the Romans. A more correct translation would have been casus causativus. Typically the case of the direct object, but also sometimes denoting "motion towards." Nouns and adjectives in French, Spanish, and Italian, languages from which English has borrowed heavily, generally were formed from the accusative case of a Latin word.
accusatory (adj.): c. 1600, from Latin accusatorius, from accusare (see accuse).
accuse (v.): c. 1300, "charge (with an offense, etc.), impugn, blame," from Old French acuser "to accuse, indict, reproach, blame" (13c.), earlier "announce, report, disclose" (12c.), or directly from Latin accusare "to call to account, make complaint against, reproach, blame; bring to trial, prosecute, arraign indict," from ad causa (see ad- + cause (n.)). Related: Accused; accusing; accusingly.
accused (n.): "person charged with a crime," 1590s, from past participle of accuse (v.).
accustom (v.): early 15c., from Old French acostumer (12c., Modern French accoutumer), from à "to" (see ad-) + costume (see costume (n.)). Related: Accustomed; accustoming.
accustomed (adj.): late 15c., "made customary, habitual," past participle adjective from accustom (v.).
ace (n.): c. 1300, "one at dice," from Old French as "one at dice," from Latin as "a unit, one, a whole, unity;" also the name of a small Roman coin ("originally one pound of copper; reduced by depreciation to half an ounce" [Lewis]), perhaps originally Etruscan and related to Greek eis "one" (from PIE *sem- "one, as one"), or directly from the Greek word.

In English, it meant the side of the die with only one mark before it meant the playing card with one pip (1530s). Because this was the lowest roll at dice, ace was used metaphorically in Middle English for "bad luck" or "something of no value;" but as the ace is often the highest playing card, the extended senses based on "excellence, good quality" arose 18c. as card-playing became popular. Ace in the hole in the figurative sense of "concealed advantage" is attested from 1904, from crooked stud poker deals.

Meaning "outstanding pilot" dates from 1917 (technically, in World War I aviators' jargon, one who has brought down 10 enemy planes, though originally in reference to 5 shot down), from French l'ace (1915), which, according to Bruce Robertson (ed.) "Air Aces of the 1914-1918 War" was used in prewar French sporting publications for "top of the deck" boxers, cyclists, etc. Sports meaning of "point scored" (1819) led to that of "unreturnable serve" (1889).
ace (v.): "to score" (in sports), 1923, from ace (n.). This led in turn to the extended student slang sense of "get high marks" (1959). Related: Aced; acing.
Aceldama: late 14c., potter's field near Jerusalem purchased with the blood-money given to Judas Iscariot, literally "place of bloodshed," from Greek Akeldama, from an Aramaic phrase akin to Syriac haqal dema "the field of blood."
acephalous (adj.): "headless," 1731, from French acéphale + -ous, or directly from Late Latin acephalus, from Greek akephalos, from a- "not" + kephale "head" (see cephalo-).