Horsepower

wiktionary

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horse +‎  power: the unit was originally defined as the amount of power that a horse could provide. 

etymonline

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horsepower (n.)

also horse-power, unit for measurement of the rate at which a motor works, 1805, from horse (n.) + power (n.); established by Watt as the power needed to lift 33,000 pounds one foot in one minute, which actually is about 1.5 times the power of a strong horse. Much abused in 19c. technical writing as "very fallacious," "shockingly unscientific," etc.