c.1400, "to invoke spirits," from Old French exorciser (14c.), from Late Latin exorcizare, from Greek exorkizein "banish an evil spirit; bind by oath" (see exorcism). Sense of "call up evil spirits to drive them out" became dominant 16c. Formerly also exorcize; a rare case where -ise trumps -ize on both sides of the Atlantic, perhaps due to influence of exercise. Related: Exorcised; exorcising.