legend vs roman-fleuve

legend

noun
  • A musical composition set to a poetical story. 

  • An inscription, motto, or title, especially one surrounding the field in a medal or coin, or placed upon a heraldic shield or beneath an engraving or illustration. 

  • A plausible story set in the historical past, but whose historicity is uncertain. 

  • The design and specification of a vessel. 

  • A person with legend-like qualities, such as extraordinary accomplishment. 

  • A fabricated backstory for a spy, with associated documents and records. 

  • A story in which a kernel of truth is embellished to an unlikely degree. 

  • A leading protagonist in a historical legend. 

  • A key to the symbols and color codes on a map, chart, etc. 

  • A cool, nice or helpful person, especially one who is male. 

  • A story of unknown origin describing plausible but extraordinary past events. 

roman-fleuve

How often have the words legend and roman-fleuve occurred in a corpus of books? (source: Google Ngram Viewer )