buyer vs travelling salesman

buyer

noun
  • A person who makes one or more purchases. 

  • A person who purchases items consumed or used as components in the manufacture of products. 

  • A person who purchases items for resale in a retail establishment. 

travelling salesman

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

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