An Etymological Dictionary of the German Language/Ungeziefer
Ungeziefer, n., ‘vermin,’ from the equiv. late MidHG. ungezī̆bere, unzī̆ver, n.; properly ‘unclean beast not suited for sacrifice.’ It is based, in fact, on OHG. ‘zëbar, ‘beast of offering,’ which is connected with the equiv. AS. tîfer. The terms borrowed in Rom., OFr. toivre, ‘cattle,’ Portug. zebro, ‘ox, cow,’ prove that zëbar was applied to large animals, and that the word was widely diffused in OTeut.