The sperm whale (Physeter macrocephalus). It has in the top of its head a large cavity, containing an oily fluid, which, after death, concretes into a whitish crystalline substance called spermaceti. See Sperm whale.
The sperm whale, hunted mainly by Yankee whalers in the South Pacific. This name comes from the French word cache, "box," which itself is the name given to a small bony section of the whale's head containing spermaceti, the precious oily substance used for making candles, ointments, and cosmetics. The English-speaking whalemen called this a "case," and because it was often a difficult place from which to extract the oil, it was sometimes called a "hard case." The man engaged in extracting it also became known as a "hard case" and so the term entered the English language for someone who is considered tough.