cognomen vs screen name

cognomen

noun
  • A nickname or epithet by which someone is identified. 

  • The third part of the name of a citizen of Ancient Rome. 

  • Surname. 

screen name

noun
  • a pseudonym used for Internet communications 

  • Synonym of stage name 

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