cryptozoic vs hidden

cryptozoic

adj
  • Hidden (especially in the soil); not easily visible. 

  • Living in a cavity or small cave. 

  • Relating to a cryptozoite. 

hidden

adj
  • Located or positioned out of sight; not visually apparent. 

  • Obscure. 

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