means A unit of power measuring the rate at which energy is used or produced, equal to one joule per second.

from Named for James Watt, the Scottish engineer who improved the steam engine in the 18th century. To sell those engines to skeptical mine and mill owners, he coined a comparison they understood — 'horsepower' — measuring how many draft horses one of his machines could replace. The unit bearing his name was adopted internationally long after his death; the cousin term 'horsepower' is his own marketing genius fossilized into physics.