commission agent vs travelling salesman

commission agent

noun
  • A merchant earning a commission by selling goods belonging to others. 

  • An agent entrusted with the possession of goods to be sold in the agent's name. 

  • A person entrusted with a confidential task, often secretly to place a bet. 

travelling salesman

noun
  • A man who travels, often within a certain territory, soliciting orders or selling goods. 

How often have the words commission agent and travelling salesman occurred in a corpus of books? (source: Google Ngram Viewer )