An Etymological Dictionary of the German Language/Annotated/weinen

by Friedrich Kluge

weinen, verb, ‘to weep, cry,’ from the equivalent Middle High German weinen, Old High German weinôn; compare Dutch weenen, Anglo-Saxon wânian, Old Icelandic veina, ‘to weep.’ Probably a derivative of the Teutonic interjection wai (see weh); hence weinen, literally ‘to lament’ (the origin of the word would be similar to that of ächzen). It is also possible that Gothic qainôn, ‘to weep, is based in the other dialects on wai, ‘woe.’