The name sperm whale is a truncation of spermaceti whale. Spermaceti, originally mistakenly identified as the whales’ semen, is the semi-liquid, waxy substance found within the whale’s head (see below).
The sperm whale is also known as the “cachalot”, which is thought to derive from the archaic French for “tooth” or “big teeth”, as preserved for example in caishau in the Gascon dialect (a word of either Romance or Basque origin). The etymological dictionary of Corominas says the origin is uncertain, but it suggests that it comes from the Vulgar Latin cappula, plural of cappulum, “sword hilt”. The word cachalot came to English via French from Spanish or Portuguese cachalote, perhaps from Galician/Portuguese cachola, “big head”. The term is retained in the Russian word for the animal, кашалот (kashalot), as well as in many other languages.

Sperm whale sketch, Wait there is still more to coloring than meets the eye.