MD vs healer

MD

noun
  • Medicinae Doctor: symbol indicating a higher research doctorate in medicine; Doctor of Medicine 

healer

noun
  • Anything that heals; a medicine that heals some wound, injury, ailment, or disease. 

  • One who heals, especially through faith. 

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