incantation vs sortilege

incantation

noun
  • The act or process of using formulas and/or usually rhyming words, sung or spoken, with occult ceremonies, for the purpose of raising spirits, producing enchantment, or creating other magical results. 

  • Any esoteric command or procedure. 

  • A formula of words used as above. 

sortilege

noun
  • Witchcraft, magic, especially as a means of making decisions or predictions. 

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