engine vs locomotive

engine

noun
  • A self-powered vehicle, especially a locomotive, used for pulling cars along a track. 

  • A person or group of people which influence a larger group; a driving force. 

  • Anything used to effect a purpose; any device or contrivance; an agent. 

  • A large construction used in warfare, such as a battering ram, catapult etc. 

  • The part of a car or other vehicle which provides the force for motion, now especially one powered by internal combustion. 

  • A complex mechanical device which converts energy into useful motion or physical effects. 

  • A software or hardware system responsible for a specific technical task (usually with qualifying word). 

locomotive

noun
  • The power unit of a train that pulls the coaches or wagons. 

  • A country which drives the world economy by having a high level of imports, such as the United States. 

  • A cheer characterized by a slow beginning and a progressive increase in speed. 

  • A traction engine. 

adj
  • Of or relating to the power unit of a train which does not carry passengers or freight itself. 

  • Of or relating to locomotion. 

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