middle name vs motto

middle name

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

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

  • One's mother's maiden name. 

motto

noun
  • A sentence, phrase, or word, forming part of an heraldic achievement. 

  • A sentence, phrase, or word, prefixed to an essay, discourse, chapter, canto, or the like, suggestive of its subject matter; a short, suggestive expression of a guiding principle; a maxim. 

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