byword vs identifier

byword

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

  • A nickname or epithet. 

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

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

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

identifier

noun
  • One who identifies as a particular type or role; one who says and believes that they are a certain thing. 

  • A formal name used in source code to refer to a variable, function, procedure, package, etc. or in an operating system to refer to a process, user, group, etc. 

  • A primary key. 

  • Someone who identifies; a person who establishes the identity of someone or something. 

  • A guidebook that helps determine the specific class of an object (such as a mushroom, herb, fish, bird, drug, or mineral), or its individual identity (such as that of a star). 

  • Something that identifies or uniquely points to something or someone else. 

  • A code that distinguishes a particular element from all other elements in a document. 

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