cornflower vs prince's feather

cornflower

noun
  • A plant of the species Cichorium intybus. 

  • Cornflower blue. 

  • A small annual plant in the family Asteraceae, Centaurea cyanus, usually with bushy blue flowers which grows natively in European cornfields (i.e. wheatfields). 

adj
  • Of a blue colour, as that of the cornflower; cornflower blue. 

prince's feather

noun
  • Amaranthus hypochondriacus, an ornamental plant. 

How often have the words cornflower and prince's feather occurred in a corpus of books? (source: Google Ngram Viewer )