code name vs eponym

code name

noun
  • A name used to clandestinely identify somebody or something, either for military or espionage purposes, or for commercial confidentiality. 

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. 

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