An Etymological Dictionary of the German Language/Annotated/weigern
weigern, verb, ‘to refuse, deny,’ from Middle High German weigern, Old High German weigarôn, ‘to oppose, refuse’; allied to Old High German weigar, ‘foolhardy,’ literally perhaps ‘obstinate, resisting.’ This is connected with the Teutonic root wī̆g, ‘to fight,’ mentioned under the preceding word.