laborer vs workhorse

laborer

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

workhorse

noun
  • Anyone or anything that does a lot of work; something or someone who works consistently or regularly. 

  • A horse used primarily for manual labor; a draft horse. 

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