köken: From Middle High German kraft, from Old High German kraft, from Proto-West Germanic *kraftu, from Proto-Germanic *kraftuz (strength, power). Cognate with Dutch kracht, Low German Kracht, English craft, Danish kraft.
aile: in der Ruhe liegt die Kraft, in Kraft, Kraftakt, Kraftausdauer, Kraftfahrzeug, Kraftgesetz, kräftig, kräftigen, kraftlos, Kraftprotz
köken: From Middle Welsh hoen, from Proto-Celtic *sognos, from Proto-Indo-European *seǵʰ- (“to overpower”), but Matasovic calls the difference in meaning "conspicuous." See the adjective hy (“bold, brave”).