blue angel vs rookie

blue angel

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

  • A mollusc of genus Glaucus. 

rookie

noun
  • A type of firecracker, used by farmers to scare rooks. 

  • A novice. 

  • An athlete either new to the sport or to a team or in his first year of professional competition, especially said of baseball, basketball, hockey and American football players. 

  • An inexperienced recruit, especially in the police or armed forces. 

adj
  • non-professional; amateur 

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