An Etymological Dictionary of the German Language/Kraft
Kraft, f., ‘strength,’ from MidHG. kraft, OHG. chraft, f., ‘strength, power, force of an army, multitude, abundance’; comp. OSax. craft, m. and f., Du. kracht; AS. crœft, m., with the HG. meanings, also ‘mental capacity, art, science,’ hence E. craft (the corresponding crafty shows prominently the last specialisation of meaning within the mental sphere); OIc. kraptr, m., ‘strength,’ ModIc. krœfr, ‘strong,’ exhibits the stem without the dental suffix; yet OIc. krefja, ‘to beg, demand, challenge,’ as well as AS. crafian, E. to crave, seems, on account of its meaning, not to be connected with the subst. No certain cognates are found in the non-Teut. languages.