1540s, "quality of being sharp or pungent in taste," from French acrimonie or directly from Latin acrimonia "sharpness, pungency of taste," figuratively "acrimony, severity, energy," abstract noun from acer "sharp" (fem. acris), from PIE root *ak- "be sharp, rise (out) to a point, pierce") + -monia suffix of action, state, condition (see -mony). Figurative extension to personal sharpness or bitterness is by 1610s.
1712, "sharp and bitter to the taste," formed irregularly (perhaps by influence of acrimonious) from Latin acer (fem. acris) "sharp to the senses, pungent, bitter; eager, fierce," also figuratively, of qualities, "active, ardent, spirited," also "hasty, quick, passionate;" of mind "violent, vehement; subtle, penetrating," from PIE *akri- "sharp," from root *ak- "be sharp, rise (out) to a point, pierce." Of feelings, temper, etc., in English from 1781. The -id suffix probably is in imitation of acid. Acrious (1670s) is a correct formation, but seldom seen. Related: Acridly.
Old English æcer "tilled field, open land," from Proto-Germanic *akraz "field, pasture" (source also of Old Norse akr, Old Saxon akkar, Old Frisian ekker, Middle Dutch acker, Dutch akker, Old High German achar, German acker, Gothic akrs "field"), from PIE root *agro- "field." "[O]riginally 'open country, untenanted land, forest'; ... then, with advance in the agricultural state, pasture land, tilled land, an enclosed or defined piece of land" [OED]. In English at first without reference to dimension; in late Old English the amount of land a yoke of oxen could plow in a day, afterward defined by statute 13c. and later as a piece 40 poles by 4, or an equivalent shape [OED cites 5 Edw. I, 31 Edw. III, 24 Hen. VIII]. The older sense is retained in God's acre "churchyard." The Germanic word was adopted early in Old French and Medieval Latin, hence the Modern English spelling, which by normal development would be *aker (compare baker from Old English bæcere).
mid-13c., aquiten, "repay, reciprocate, reward or retaliate for" (a good or bad deed); c. 1300 as "satisfy a debt; redeem (a pledge)," from Old French aquiter, acquiter "pay, pay up, settle a claim" (12c., Modern French acquitter), from a- "to" (see ad-) + quite "free, clear," from Medieval Latin quitus, quittus, from Latin quietus "free" (in Medieval Latin "free from war, debts, etc."), also "calm, resting" (from PIE root *kweie- "to rest, be quiet"). Also in part from Medieval Latin acquitare. From mid-14c. as "relieve (someone) of an obligation, release from a pledge," hence the meanings "set (an accused person) free from charges, pronounce not guilty," and "discharge one's duty; behave or conduct oneself" (for better or worse), all of which date to late 14c. The notion in the word is "to release or discharge," from an obligation or from accusation, guilt, censure, or suspicion. Related: Acquitted; acquitting.
late 14c., adquisicioun, "act of obtaining," from Old French acquisicion "purchase, acquirement" (13c., Modern French acquisition) or directly from Latin acquisitionem (nominative acquisitio), noun of action from past-participle stem of acquirere "get in addition, accumulate," from ad "to," here perhaps emphatic (see ad-), + quaerere "to seek to obtain" (see query (v.)). The meaning "thing obtained" is from late 15c. The vowel change of -ae- to -i- in Latin is due to a phonetic rule in that language involving unaccented syllables in compounds.