An Etymological Dictionary of the German Language/Aussatz
Aussatz, m., from the equiv. late MidHG. ûȥ-satz, m., ‘leprosy’; a singular, late and regressive formation from the MidHG. subst. ûȥsetze and ûȥsetzel, ‘leper,’ MidHG. ûȥsetzig, adj., ‘leprous,’ OHG. ûȥ-sâzzo, ûȥ-sâzeo, m., ‘leper’; lit. ‘one who lives outside, separate’; those who were afflicted with leprosy were exposed. Considering the very late appearance of the subst. Aussatz, in contrast to the early OHG. ûȥsâzeo, ‘leper,’ there is no doubt that Aussatz is a recent formation, like Ärger from ärgern. The Goth. word for leprosy is þrutsfill.