backstory vs delusion

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. 

delusion

noun
  • The state of being deluded or misled, or process of deluding somebody. 

  • A false belief that is resistant to confrontation with actual facts. 

  • A fixed, false belief, that will not change, despite evidence to the contrary. 

  • That which is falsely or delusively believed or propagated; false belief; error in belief. 

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