late 14c., "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.)). 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.
