blue bonnet vs cornflower

blue bonnet

noun
  • Any of several blue flowering plants, especially cornflower, Centaurea cyanus, and plants of the genus Scabiosa. 

  • A blue Australian parrot, especially Northiella haematogaster. 

  • A traditional flat Scottish hat made of blue wool; a blue tam-o'-shanter. 

  • Someone who wears such a hat; a Scotsman, especially a Scottish soldier. 

  • Any of several North American species of Lupinus common in the southwestern US, especially Lupinus texensis and Lupinus subcarnosus. 

cornflower

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

  • Cornflower blue. 

  • A plant of the species Cichorium intybus. 

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

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