combine harvester vs reaper

combine harvester

noun
  • A combine, a farming machine that harvests, threshes, and cleans grain plants. 

reaper

noun
  • A machine used to harvest crops. 

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

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

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