late 14c., from Old French esposailles (plural) "act of betrothal" (12c., Modern French époussailles), from Latin sponsalia "betrothal, espousal, wedding," noun use of neuter plural of sponsalis "of a betrothal," from sponsa "spouse" (see espouse). For the -e- see e-. Figuratively, of causes, principles, etc., from 1670s.
