novella vs saga

novella

noun
  • A short novel or long short story. 

  • Synonym of novel (“new legal constitution in Ancient Rome”) 

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. 

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