iridescence vs polychromasia

iridescence

noun
  • The condition or state of being iridescent; exhibition of colors like those of the rainbow; a prismatic play of color. 

  • Any shimmer of glittering and changeable colors. 

polychromasia

noun
  • A disorder in which there is an abnormally high number of red blood cells in the bloodstream as a result of their having been prematurely released from the bone marrow during blood formation. 

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