reaper vs the pale rider

reaper

noun

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

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

  • A machine used to harvest crops. 

the pale rider

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