cognomen vs nom de Web

cognomen

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

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

  • Surname. 

nom de Web

noun
  • A pseudonym used when publishing on the World Wide Web. 

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