An Etymological Dictionary of the German Language/Annotated/hagen
hagen, behagen, verb, from the equivalent Middle High German hagen, behagen, ‘to please, gratify,’ Old High German *bihagôn: compare Old Saxon bihagôn, Anglo-Saxon onhagian, ‘to please, suit.’ The stem hag, ‘to suit,’ is widely diffused in Old Teutonic, and its strong participle is preserved in Old High German and Middle High German (gihagan and behagen, ‘suitable’). Allied to Scandinavian hagr, adjective, ‘skilful,’ hagr, masculine, ‘state, situation, advantage,’ hœgr, ‘suitable.’ The root hag, from pre-Teutonic kak, corresponds to the Sanscrit root çak, ‘to be capable, able, conducive,’ whence çakrá, ‘strong, helpful.’