An Etymological Dictionary of the German Language/oder
oder, conj., from the equiv. MidHG. oder, OHG. odar, ‘or, else’; the OHG. and MidHG. ordinary form are without r; OHG. odo, earlier ëddo, MidHG. ode, od. This abnormal r is, according to some, a compar. suffix; according to others it is simply an suffix due to the influence of OHG. wëdar, MidHG. wëder, ‘neither.’ OHG. ëddo, ëdo, correspond further to Goth. aíþþau, ‘or,’ which is a compound of Goth. iþ, ‘and’ (Lat. et), and þau, ‘or.’ E. or has no connection with this word, since it originated in AS. âhwœþer; Goth. aíþþau is AS. oþþe and ëþþa, ‘or,’ which became obsolete ar an early period.