An Etymological Dictionary of the German Language/Annotated/weder
Appearance
weder, particle, in conjunction with noch, from Middle High German newëder, Old High German niwëdar; this is properly a neuter of wëdar, ‘each of two,’ niwëdar... noh, ‘neither of the two... nor.’ Compare the corresponding development of entweder, and also English either (literally ‘each of two’).