covert vs cryptozoic

covert

adj
  • Secret, surreptitious, concealed. 

  • Under coverture. 

noun
  • A covering. 

  • A disguise. 

  • A feather that covers the bases of flight feathers. 

  • Area of thick undergrowth where animals hide. 

  • A hiding place. 

cryptozoic

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

  • Living in a cavity or small cave. 

  • Relating to a cryptozoite. 

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