sneaker vs stool pigeon

sneaker

noun
  • One who sneaks. 

  • A sneaker male. 

  • An athletic shoe with a soft, rubber sole. A trainer. 

stool pigeon

noun
  • An informer to the authorities, especially one who gives up criminal associates. 

  • A pigeon tied to a stool by a piece of twine, used as a decoy to entice free-flying birds to the ground to be shot or trapped. 

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