An Etymological Dictionary of the German Language/schlimm
schlimm, adj., ‘bad, wicked,’ from MidHG. slimp, adj., ‘awry, aslant,’ whence the adv. slimbes, ‘obliquely’; OHG. *slimb, ‘aslant,’ may be assumed from the derivative abstr. form slimbî, ‘slope.’ The moral signification of the adj. first occurs in ModHG.; a similar development is seen in Du. slim, ‘bad’ (beside which occurs slimbeen, ‘person with bandy-legs’). E. slim and OIc. slœ́mr, ‘vile,’ were borrowed from the Continent. The remoter history of OTeut. slimba-, ‘aslant, awry,’ from which Ital. sghembo, ‘awry, bent,’ was borrowed at an early period, is quite obscure.