An Etymological Dictionary of the German Language/krumm
krumm, adj., ‘crooked,’ from MidHG. krump(b), OHG. chrumb, ‘crooked, curved, twisted, perverted’ (comp. kraus); rare variants OHG. and MidHG. krumpf, OHG. chrampf, as well as MidHG. krimpf, in the same sense. Comp. OSax. crumb, AS. crumb; E. crump, ‘crooked,’ is abnormal (with this E. to crumple, MidE. crumpeln, and also E. crimple, ‘wrinkle, fold,’ are connected). Under Krampf it is shown how the graded and permutated forms are widely ramified; the Teut. root signified ‘spasmodically contracted, curved.’ Besides the cognates of West Teut. krumba-, from pre-Teut. grumpó-, quoted under Krampf, comp. the unnasalised Gr. γρῦπός, ‘curved, bent’?. OIr. cromm, W. crwm, seem to have been borrowed from AS.