Pachyderm is a term used to describe all those grey, thick-skinned giant mammals you usually see at the zoo, chiefly the rhinoceros, hippopotamus, and elephant. That quality of having thick skin is going to be important in a moment, so pay attention. We got the word in 1838 from French pachyderme, where it was used as a biological term to classify the animals. This in turn was taken from Greek pakhydermos, which translates to "thick-skinned", which makes sense for the aforementioned reason. Pakhydermos is a portmanteau of pakhys, meaning "large", and derma, that root pertaining to skin that we all recognize from the word dermatologist. Pakhys is reconstructed as coming from the Proto-Indo-European root beng, which could carry connotations of either "thick" or "fat". Derma, meanwhile, came from PIE der, which meant "to split", a definition that was connected to "skin" by an intermediate translation of "flay".
Adam Aleksic, a freshman studying linguistics at Harvard University, has been described as the internet's sixth most famous etymologist. He has disturbing interests in words, vexillology, geography, board games, limericks, and law, and he loves writing about himself in the third person.
The Etymology Nerd