backstory vs mythology

backstory

noun
  • A fictitious account of a person's history designed to conceal their actual history and motives. 

  • The previous life and experiences of a person, especially a character in a dramatic work, but also a real-life person. 

  • A prequel. 

mythology

noun
  • A similar body of myths concerning an event, person or institution. 

  • Pervasive elements of a fictional universe that resemble a mythological universe. 

  • The collection of myths of a people, concerning the origin of the people, history, deities, ancestors and heroes. 

  • The systematic collection and study of myths. 

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