family name vs pen name

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. 

pen name

noun
  • A fictitious name used by an author in place of their actual name; a writer's pseudonym. 

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