shunting engine vs switcher

shunting engine

noun
  • A locomotive that carries out shunting duties. 

switcher

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

  • A switchmode power supply. 

  • Synonym of vision mixer (“device for selecting between video sources”) 

  • One who or that which operates a switch. 

  • One who or that which switches, or changes to something else. 

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