eponym vs family name

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. 

family name

noun
  • A given name common in a family, or already borne by someone in the family (in the context of naming someone in the family after that family member). 

  • A surname. 

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