fiction vs figment of one's imagination

fiction

noun
  • Literary type using invented or imaginative writing, instead of real facts, usually written as prose. 

  • A verbal or written account that is not based on actual events (often intended to mislead). 

  • A legal fiction. 

figment of one's imagination

noun
  • A product of the imagination. 

How often have the words fiction and figment of one's imagination occurred in a corpus of books? (source: Google Ngram Viewer )