epitaph vs motto

epitaph

noun
  • A poem or other short text written in memory of a deceased person. 

  • An inscription on a gravestone in memory of the deceased. 

verb
  • To write or speak after the manner of an epitaph. 

  • To commemorate by an epitaph. 

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 epitaph and motto occurred in a corpus of books? (source: Google Ngram Viewer )