What's the "een" in Halloween?
early 15c., "military campaign; the act of rapidly setting forth," from Middle French expédition (13c.) and directly from Latin expeditionem (nominative expeditio), noun of action from past participle stem of expedire (see expedite). Meaning "journey for some purpose" is from 1590s. Sense by 1690s also included the body of persons on such a journey. Related: Expeditionary.