demigod vs protagonist

demigod

noun
  • Someone held up for reverence as a supreme example. 

  • A half-god or hero; the offspring of a deity and a mortal. 

protagonist

noun
  • An advocate or champion of a cause or course of action. 

  • The main character, or one of the main characters, in any story, such as a literary work or drama. 

  • A leading person in a contest; a principal performer. 

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