An Etymological Dictionary of the German Language/Annotated/Ungeziefer
Ungeziefer, neuter, ‘vermin,’ from the equivalent late Middle High German ungezī̆bere, unzī̆ver, neuter; properly ‘unclean beast not suited for sacrifice.’ It is based, in fact, on Old High German ‘zëbar, ‘beast of offering,’ which is connected with the equivalent Anglo-Saxon tîfer. The terms borrowed in Romance, Old French toivre, ‘cattle,’ Portug. zebro, ‘ox, cow,’ prove that zëbar was applied to large animals, and that the word was widely diffused in Old Teutonic.