強力
きょうりょく · kyouryoku · JLPT N3 · na-adj
strong
💪 強力 = strong + power: strength stacked on strength
強 (きょう) means strong and 力 (りょく) means power or force, the same 力 found in 努力 (effort) and 能力 (ability). Two strength kanji side by side give you powerful.
力 — pictograph of a plow or arm muscle
力 originated as a pictograph of an ancient plow, the main tool requiring physical exertion in early agriculture. Some scholars also see it as a flexed arm showing muscle. From this concrete image it broadened to mean 'strength, power, force, effort'.