Druid vs witch doctor

Druid

noun
  • A member of a benefit society founded in 1781, the Ancient Order of Druids. 

witch doctor

noun
  • A person (often male) who is believed to ward off witchcraft and heal through magical powers; a shaman. 

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