byword vs proper noun

byword

noun
  • A characteristic word or expression; a word or phrase associated with a person or group. 

  • A nickname or epithet. 

  • Someone or something that stands as an example (i.e. metonymically) for something else, by having some of that something's characteristic traits. 

  • A proverb or proverbial expression, common saying; a frequently used word or phrase. 

  • An object of notoriety or contempt, scorn or derision. 

proper noun

noun
  • A word or phrase that is a noun denoting a particular person, place, organization, ship, animal, event, or other individual entity. 

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