The mastodon was named in 1813 by Georges Cuvier, who clearly had his mind on one thing. To create this new genus name, Cuvier combined the Greek word mastos, meaning "breast", and "dontos", meaning "tooth". The word itself literally had the denotation of "breast-tooth", and was meant to describe how mastodon teeth have tiny nubs on their teeth, not altogether un-mammary-esque. Mastos (which in Greek was particular to the female breast, and you may recognize it from mastectomy) comes from the Proto-Indo-European word mad, or "dripping", a connection to milk. Meanwhile, dontos is directly from the Proto-Indo-European root dent, which meant "teeth", plural. You may recognize it from orthodontics and other such terms. Usage of the word mastodon is on the decline since the early twentieth century.
Adam Aleksic, a rising sophomore studying linguistics and government at Harvard University, has been described as the internet's sixth most famous etymologist. He also has disturbing interests in politics, vexillology, geography, board games, conlanging, and law.