adverbial phrase vs motto

adverbial phrase

noun
  • A phrase that collectively modifies a verb, adjective, another adverb, or a prepositional phrase. 

motto

noun
  • 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. 

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

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