An Etymological Dictionary of the German Language/Annotated/opfern
opfern, verb, from the equivalent Middle High German opfern, Old High German opfarôn, ‘to sacrifice’; so too Old Saxon offrón, Dutch offeren, Anglo-Saxon offrian, ‘to sacrifice,’ whence English to offer, under the influence of French offrir. Introduced by the Church from Latin offerre. With regard to the change of accent in Teutonic, compare predigen, from praedicare, in which the verbal particle likewise assumed the accent. —