parchment vs tegument

parchment

noun
  • The creamy to tanned color of parchment. 

  • A document made on such material. 

  • Material, made from the polished skin of a calf, sheep, goat or other animal, used like paper for writing. 

  • The envelope of the coffee grains, inside the pulp. 

  • Stiff paper imitating that material. 

  • A diploma (traditionally written on parchment). 

tegument

noun
  • Something which covers; a covering or coating. 

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