shopkeeper vs travelling salesman

shopkeeper

noun
  • A trader who sells goods in a shop, or by retail, in distinction from one who sells by wholesale, or sells door to door. 

travelling salesman

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

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