saga vs work of fiction

saga

noun
  • Something with the qualities of such a saga; an epic, a long story. 

  • An Old Norse (Icelandic) prose narrative, especially one dealing with family or social histories and legends. 

work of fiction

noun
  • A fictional account; a story. 

  • A fictitious account; an account of events that never took place. 

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