necromancy vs voodooism

necromancy

noun
  • Loosely, any sorcery or witchcraft, especially involving death or the dead, particularly sorcery involving raising or reanimating the dead. 

  • Synonym of necroposting 

  • Divination involving the dead or death. 

voodooism

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

  • Any voodoo practice. 

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