late 14c., "evenness, smoothness, uniformity;" c.1400, in reference to amount or number, from Old French equalité "equality, parity" (Modern French égalité, which form dates from 17c.), from Latin aequalitatem (nominative aequalitas) "equality, similarity, likeness" (also sometimes with reference to civil rights), from aequalis "uniform, identical, equal" (see equal, adj.). Early 15c. as "state of being equal." Of privileges, rights, etc., in English from 1520s.