勢力
せいりょく · seiryoku · JLPT N1 · noun
influence
勢 (momentum, force) + 力 (strength) = 勢力 (influence, might)
勢 means momentum or the force of a moving current, and 力 means strength. Together they describe the pull a strong force exerts over others, which is influence or power.
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'.