bobby vs signaller

bobby

noun
  • A railway signaller. 

  • A banana that is extra small in size. 

  • A penis. 

  • A police officer. 

  • A calf that is slaughtered in its first month, usually because it has no mother or because it is undersized or otherwise defective. 

  • Cocaine. 

signaller

noun
  • synonym of signalman 

  • One who signals. 

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