An Etymological Dictionary of the German Language/Euter
Euter, m. and n., ‘udder, dug,’ from the equiv. MidHG. iuter, ûter, OHG. ûtar, ûtiro, m.; a word common to Teut. and orig. a primit. Aryan word, which has the same sense everywhere. Comp. Du. uijer, AS. ûder, E. udder; also with gradation eudar in MidLG. jeder, OFris. iader, OIc. júgr. The-resulting Teut. ûdr-, eudr-, from Aryan ûdhr-, corresponds to the equiv. Sans. ûdhar, Gr. οὔθαρ (with gradation), Lat. ûber; Slav. vymę (from *vyd-men-), ‘udder,’ is differently derived.