An Etymological Dictionary of the German Language/Annotated/schlimm
schlimm, adjective, ‘bad, wicked,’ from Middle High German slimp, adjective, ‘awry, aslant,’ whence the adverb slimbes, ‘obliquely’; Old High German *slimb, ‘aslant,’ may be assumed from the derivative abstract form slimbî, ‘slope.’ The moral signification of the adjective first occurs in Modern High German; a similar development is seen in Dutch slim, ‘bad’ (beside which occurs slimbeen, ‘person with bandy-legs’). English slim and Old Icelandic slœ́mr, ‘vile,’ were borrowed from the Continent. The remoter history of Old Teutonic slimba-, ‘aslant, awry,’ from which Italian sghembo, ‘awry, bent,’ was borrowed at an early period, is quite obscure.