cognomen

Noun

• the name used to identify the members of a family (as distinguished from each member's given name)

• a familiar name for a person (often a shortened version of a person's given name)
  • Joe's mother would not use his nickname and always called him Joseph
    
  • Henry's nickname was Slim
    

Related words

• Synonyms: 
  surname , family name , last name , nickname , moniker , sobriquet , soubriquet , byname