Etymologically
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horsepower

This is the current revision of this entry, as edited by bogdan on 31 October 2026 at 11:13. This address is a permanent link to this version.
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Pronunciation

  • /ˈhɔɹsˌpaʊɚ/, /ˈhɔːsˌpaʊə/[1]

Etymology

It is formed from English horse + power,[2][3][4][5] from the supposed rate at which a horse works.[4] According to Etymonline, the unit was set by James Watt as the power needed to lift 33,000 pounds one foot in one minute, which is about one and a half times the power of a strong horse.[3]

Earliest recorded meaning

The power of a horse in drawing, and a conventional unit for the rate of work of an engine: 1806, in O. G. Gregory's Treatise of Mechanics;[2][6] Etymonline dates it 1805.[3]

Semantic evolution

From 1823 the word was used with a number to give the power of an engine, as in Byron's note to Don Juan.[2] From 1859 it was used with qualifying words such as brake horsepower and indicated horsepower.[2][4] From 1853 it also meant the work of horses used to drive machinery, and a machine worked by a horse.[2][6] Transferred and figurative uses, power in general, followed in 1860.[2][4] Etymonline notes that 19th-century technical writers called the unit "very fallacious" and "shockingly unscientific".[3]

Timeline

  • 1805 – the unit of power, in Etymonline.[3]
  • 1806 – the rate of work of a horse; a unit of the rate of work of an engine.[2][6]
  • 1823 – with a numeral, the power of an engine.[2]
  • 1853 – a machine driven by a horse.[2]
  • 1859 – brake horsepower, indicated horsepower.[2]
  • 1860 – transferred and figurative, power in general.[2]

Meanings

Noun

  1. A unit of power equal to 550 foot-pounds per second, or about 746 watts.[7][6][4]
  2. The power of an engine or motor measured in this unit: a 200-horsepower outboard.[2][6]
  3. Effective power or capability.[6][2]
  4. A machine worked by a horse.[6][2]

Word family

  • horsepower-hour
  • brake horsepower
  • shaft horsepower

References

  1. ^ Wiktionary, the free dictionary, https://en.wiktionary.org
  2. ^ a b c d e f g h i j k l m n Oxford English Dictionary Online (accessed March 2026), Oxford: Oxford University Press
  3. ^ a b c d e Harper, Douglas. Online Etymology Dictionary, https://www.etymonline.com
  4. ^ a b c d e Shorter Oxford English Dictionary on Historical Principles (2002), 5th ed., ed. William R. Trumble and Angus Stevenson, Oxford: Oxford University Press
  5. ^ Dictionary.com Unabridged (2016), based on the Random House Unabridged Dictionary, New York: Random House
  6. ^ a b c d e f g Merriam-Webster Unabridged Dictionary (2024), online ed., Springfield, Mass.: Merriam-Webster
  7. ^ Collins English Dictionary (2023), Glasgow: HarperCollins