Etymologically

castor

Etymology and origin of the English word castor

Pronunciation

  • IPA: /ˈkɑːs.tə/ (UK); /ˈkæs.tɚ/ (US)[1]

Etymology

It comes from Middle English,[2][3] from Old French castor[4][5] and from Latin castor (“beaver”),[2][4][5][3][6] from Ancient Greek κάστωρ (kástōr, “beaver”),[2][4][5][3][6] which was identified with Kástōr, the name of one of the divine twins.[4][5][3] Castor was worshipped by women in ancient Greece as a healer, and the beaver's secretion was used medicinally,[4][5] but Etymonline notes that the animal did not live in classical Greece, so the word was probably borrowed from another language.[5]

Earliest recorded meaning

The beaver (before 1398).[4][5][7]

Semantic evolution

From 1601 the word meant the strong-smelling substance from the beaver's glands, also called castoreum,[7] used in medicine and perfume.[2][6] A hat of beaver fur was a castor from 1640,[7] and the name was then given to a heavy woollen cloth.[7][2][6] Castor oil (1746), from a plant, perhaps took its name from a likeness in use to castoreum.[4][5] The spelling castor is also used for the furniture wheel and sprinkler properly called a caster.[2][7][6]

Timeline

  • before 1398 – the beaver.[4][7]
  • 1601 – castoreum.[7]
  • 1640 – a beaver hat.[7]
  • 1746 – castor oil.[4]

Modern meaning

Noun

  1. An oily, strong-smelling substance from glands in the groin of the beaver, used as a fixative in perfume; castoreum.
  2. A hat of beaver fur or an imitation of it.
  3. A heavy woollen cloth used for overcoats.
  4. (archaic) A beaver.
  5. A variant spelling of caster, a small wheel or a sprinkling container.

Proper noun

  1. In Greek mythology, one of the twin Dioscuri, brother of Pollux.
  2. A double star in the constellation Gemini.

Word family

  • castor sugar
  • castoreum
  • castor oil
  • caster
  • beaver

References

  1. ^ Wiktionary, the free dictionary, https://en.wiktionary.org
  2. ^ a b c d e f The American Heritage Dictionary of the English Language (1992), 3rd ed., Boston: Houghton Mifflin
  3. ^ a b c d Merriam-Webster's Collegiate Dictionary (2003), 11th ed., Springfield, Mass.: Merriam-Webster
  4. ^ a b c d e f g h i Barnhart, Robert K., ed. (1995), The Barnhart Concise Dictionary of Etymology, New York: HarperCollins
  5. ^ a b c d e f g h Harper, Douglas, Online Etymology Dictionary, https://www.etymonline.com
  6. ^ a b c d e Random House Webster's Unabridged Dictionary (1999), 2nd ed., New York: Random House
  7. ^ a b c d e f g h Simpson, J. A.; Weiner, E. S. C., eds. (1989), The Oxford English Dictionary, 2nd ed., Oxford: Clarendon Press

Related etymologies

Cite this entry

“Castor.” Etymologically, 11 Oct. 2026, etymologically.com/en/castor. Accessed 11 Oct. 2026.

Last edited on . ·