An Etymological Dictionary of the German Language/Annotated/Schelm
Schelm, masculine, ‘rogue, knave, villain,’ from Middle High German schęlme, masculine, ‘pest, plague; those who have fallen in battle,’ then, as an abusive term, ‘wretch, seducer,’ Old High German scalmo, scęlmo, ‘plague.’ In Middle Dutch and Middle Low German schelm has the old sense of ‘carrion, cadaver,’ so too in Bavarian. For the development of the meaning ‘rogue’ from ‘wretch,’ compare Schalf, which has also acquired a milder signification. From the Modern High German word are derived Dutch schelm and Icelandic skelmir, ‘rogue.’