derm vs epidermis

derm

noun
  • The integument of animal; the skin. 

  • Synonym of dermis. 

  • Guts, entrails. 

epidermis

noun
  • The outer, protective layer of the skin of vertebrates, covering the dermis 

  • The similar outer layer of cells in invertebrates and plants 

How often have the words derm and epidermis occurred in a corpus of books? (source: Google Ngram Viewer )