Yours, Etc.: Origins and Uses of 8 Sign-Offs
late 14c., from Latin aequalis "uniform, identical, equal," from aequus "level, even, just," of unknown origin. Parallel formation egal (from Old French egal) was in use late 14c.-17c. The noun is recorded from 1570s.
1580s, "compare, liken," also "match, rival," from equal (adj.). Related: Equaled; equaling.