An Etymological Dictionary of the German Language/schwach

by Friedrich Kluge

schwach, adj., ‘weak, infirm, feeble,’ from MidHG. swach, adj., ‘low, poor, despised, weak, infirm’; wanting in OHG. as well as in the other Teut. dials. The usual derivation from a Teut. root swek, ‘to swell’ (schwach, orig. ‘that which has lost its savour’), must be abandoned; schwach is rather allied to siech, so that the Teut. roots suk, swak, are to be assumed (comp. the following word).