iniquity (n.)

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.

late 14c., "identical in amount, extent, or portion;" early 15c., "even or smooth of surface," from Latin aequalis "uniform, identical, equal," from aequus "level, even, flat; as tall as, on a level with; friendly, kind, just, fair, equitable, impartial; proportionate; calm, tranquil," which is of unknown origin. Parallel formation egal (from Old French egal) was in use late 14c.-17c. Equal rights is from 1752; by 1854 in American English in reference to men and women. Equal opportunity (adj.) in terms of hiring, etc. is recorded by 1925.