cameo vs protagonist

cameo

noun
  • A single very brief appearance, especially by a prominent celebrity in a movie or song. 

  • A piece of jewelry, etc., carved in relief. 

verb
  • To appear in a cameo role. 

protagonist

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

  • 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. 

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