plower vs reaper

plower

noun
  • One who plows; one who works land with a plow. 

reaper

noun
  • One who reaps; a person employed to harvest crops from the fields by reaping. 

  • The recluse spider (Loxosceles and Sicarius spp.). 

  • A machine used to harvest crops. 

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