middle name vs sobriquet

middle name

noun
  • A name between the first given name and the family name or surname; a second or subsequent given name. 

  • A trait, activity, or action closely associated with or aptly describing a person. 

  • One's mother's maiden name. 

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 middle name and sobriquet occurred in a corpus of books? (source: Google Ngram Viewer )