努力
どりょく · doryoku · JLPT N3 · noun
effort
💪 努力 = strive + strength: putting all your power into trying
努 means to strive or exert yourself, and it already contains 力 (strength) at its base. 力 then repeats it: strength on top of strength. Doryoku is the word for hard work, as in 努力する, to make an effort.
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'.