late Middle English (as a noun denoting an ecclesiastical decree): from French, from Latin sanctio(n-), from sancire 'ratify'. The verb dates from the late 18th century
Sanction is confusing because it has two meanings that are almost opposite. In most domestic contexts, sanction means ‘approval, permission’: voters gave the measure their sanction. In foreign affairs, sanction means ‘penalty, deterrent’: international sanctions against the republic go into effect in January.