laborer vs plodder

laborer

noun
  • One who uses body strength instead of intellectual power to earn a wage, usually hourly. 

plodder

noun
  • A person who works slowly, making a great effort with little result; a person who studies laboriously. 

  • One who plods. 

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