An Etymological Dictionary of the German Language/Annotated/gegen
gegen, preposition, ‘against, opposite to, in presence of, in comparison with,’ from Middle High German gęgen, Old High German gęgin, gagan, ‘against’ (in Old High German and Middle High German almost always with a dative); allied to the Middle High German adverb gęgene, Old High German gęgini, gagani, ‘towards’; corresponding to Anglo-Saxon geán, ongeán, ‘against,’ English again; Old Saxon gęgin and Old Icelandic gagn, ‘against,’ appear only in compounds; in Gothic a corresponding word is wanting. Of obscure origin. —