herbalist vs shaman

herbalist

noun
  • A person who treats diseases by means of medicinal herbs. 

shaman

noun
  • A traditional (unscientific) faith healer. 

  • A member of certain tribal societies who acts as a spiritual and, or religious medium between the concrete and spirit worlds. 

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