family name vs sobriquet

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. 

sobriquet

noun
  • A familiar name for a person or thing; a nickname (sometimes assumed by the person, but often given by others), that is descriptive. 

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