backstory vs biography

backstory

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

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

  • A prequel. 

biography

noun
  • A person's life story, especially one published. 

  • The art of writing this kind of story. 

verb
  • To write a biography of. 

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