demonology vs voodooism

demonology

noun
  • The study of demons, especially the incantations required to summon and control them. 

voodooism

noun
  • Any voodoo practice. 

  • A religious cult, from Haiti, involving witchcraft and sorcery. 

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