1563, "confirmation or enactment of a law," from L.
sanctionem (nom.
sanctio) "act of decreeing or ordaining," also "decree, ordinance," from
sanctus, pp. of
sancire "to decree, confirm, ratify, make sacred" (see
saint). Originally especially of ecclesiastical decrees. The verb sense of "to permit authoritatively" is from 1797.
Sanctions, in international diplomacy, first recorded 1919, from
sanction (n.) in the sense of "part or clause of a law which spells out the penalty for breaking it" (1651).