autonym vs pet name

autonym

noun
  • An infraspecific name in which the specific epithet is repeated. 

  • A name used by a group or category of people to refer to themselves or their language, as opposed to a name given to them by other groups. 

  • A work published under the author's true name. 

  • The true name of a person or other entity, especially an author. 

pet name

noun
  • A nickname, especially a name used by those in love with one another. 

  • Used other than figuratively or idiomatically: see pet, name. 

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