dispatcher vs mediator

dispatcher

noun
  • In a transportation organization, a person who controls the movements of vehicles. 

  • Any die used for cheating, whether fraudulently weighted or bearing duplicate numbers. 

  • A piece of software responsible for assigning priorities and resources to tasks waiting to be scheduled. 

mediator

noun
  • One who negotiates between parties seeking mutual agreement. 

  • A chemical substance transmitting information to a targeted cell. 

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