shunter vs shunting engine

shunter

noun
  • A railway locomotive used for shunting; a switcher. 

  • A person who carries out shunting operations. 

  • One who shunts (carries on arbitrage between London and provincial stock exchanges). 

shunting engine

noun
  • A locomotive that carries out shunting duties. 

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