allonym vs pseudonym

allonym

noun
  • A pseudonym, (particularly) another person's name used as a pseudonym by the author of a work. 

  • An allonymous work: a book published under the name of a person other than its true author. 

pseudonym

noun
  • A fictitious name (more literally, a false name), as those used by writers and movie stars. 

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