cryptozoic vs spectral

cryptozoic

adj
  • Relating to a cryptozoite. 

  • Living in a cavity or small cave. 

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

spectral

adj
  • Of, or pertaining to, spectres; ghostly. 

  • Of, or pertaining to, spectra; classified according to frequency or wavelength (of light etc) 

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