Old English udder "milk gland of a cow, goat, etc.," from Proto-Germanic *udr- (cognates: Old Frisian uder, Middle Dutch uyder, Dutch uijer, Old High German utar, German Euter, and, with unexplained change of consonant, Old Norse jugr), from PIE *eue-dh-r "udder" (cognates: Sanskrit udhar, Greek outhar, Latin uber "udder, breast").