They are called sperm whales because early whalers found a milky-white, waxy fluid in the whales’ huge heads and mistakenly thought it was semen, so they named both the substance “spermaceti” and the animal the “sperm whale.”

The name “spermaceti”

  • Inside a sperm whale’s massive square head is a large organ filled with a white, oily-waxy liquid now known as spermaceti.
  • When 18th–19th century whalers cut open the head, they believed this substance was sperm, which led directly to the name “sperm whale.”

Why spermaceti mattered

  • Spermaceti could be processed into high-quality candles, lamp oil, lubricants, and cosmetic products, making sperm whales commercially valuable in the whaling era.
  • This economic importance helped fix the name “sperm whale” in sailors’ language and later in scientific and popular usage.

Not about shape or behavior

  • The name is not because the whale looks like a sperm cell; that modern guess is a myth and has no historical basis.
  • Other common names like cachalot exist, but “sperm whale,” tied to spermaceti and whaling history, became the dominant term in English.

Information gathered from public forums or data available on the internet and portrayed here.