combine harvester vs mower

combine harvester

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

mower

noun
  • A farm machine used in hay production (sickle mower, finger-bar mower). 

  • A lawnmower, a machine used to cut grass on lawns. 

  • A person who cuts grass. 

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