anamnesis vs backstory

anamnesis

noun
  • The ability to recall past events; recollection. 

  • The mention of the past; quotation of exemplary authors from memory to establish one's authority. 

  • The medical history of a patient. 

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. 

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