Pachyderm comes from French pachyderme and Greek pachydermos, thick-skinned. Its components are pachys, thick, and derma, skin.
Sources
- Merriam-Webster: pachyderm
Word History gives both roots and the French route; the definition identifies the former group, and the usage note explains figurative pachydermatous.
- Online Etymology Dictionary: hypodermic
Hypodermic: from hypo- “under” + *derma* “skin” + -ic
- Online Etymology Dictionary · pachyderm
Meanings of the older forms on the word path.