blue angel vs cerulean

blue angel

noun
  • A blue flame produced by lighting one's flatus. 

  • A mollusc of genus Glaucus. 

cerulean

noun
  • A greenish-blue color. 

  • Any of various lycaenid butterflies of the genus Jamides. 

adj
  • Sky-blue. 

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