Huh, TIL.

The whale’s common name originated during the heyday of the commercial whaling industry, from the end of the 18th century through the 19th century. The head of the sperm whale contains an enormous fluid-filled organ (which whalers called the case). During whale harvests, this organ, now called the spermaceti organ, was discovered to contain a white liquid that whalers mistook for the sperm of the whale. The spermaceti organ is unique to sperm whales, although bottlenose whales possess a similar organ. It has a volume as large as 2,000 liters (530 gallons) and can extend through 40 percent of the whale’s length.

https://www.britannica.com/story/how-did-the-sperm-whale-get-its-name