kafir vs non-Muslim

kafir

noun
  • A disbeliever, a denier: someone who rejects or disbelieves in God as per Islam (Arabic: الله Allāh) or the tenets of Islam; or more broadly any non-Muslim. 

non-Muslim

noun
  • One who is not a Muslim. 

adj
  • Not Muslim. 

How often have the words kafir and non-Muslim occurred in a corpus of books? (source: Google Ngram Viewer )