coalman vs digger

coalman

noun
  • Someone who delivers coal. 

  • A coal miner (as distinguished from other type of miners). 

  • Someone who sells coal. 

digger

noun
  • A large piece of machinery that digs holes or trenches. 

  • A tool for digging. 

  • A spade (playing card). 

  • An Australian soldier. 

  • One who digs. 

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