eponym vs nom de clavier

eponym

noun
  • A real or fictitious person's name that has given rise to the name of a particular item. 

  • A word formed from a real or fictive person’s name. 

  • A word formed from a real or fictive place or thing. 

nom de clavier

noun
  • A pseudonym used in online communications; a handle. 

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