stool pigeon vs tattler

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. 

tattler

noun
  • One who tattles (notifies authorities of illicit behavior) or is inclined to do so; a tattletale. 

  • Either of two similar bird species in the shorebird genus Heteroscelus (Tringa in some taxonomies). 

  • A device fitted to a vehicle to measure mileage etc. 

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