proverb vs watchword

proverb

noun
  • A phrase expressing a basic truth which may be applied to common situations. 

  • A striking or paradoxical assertion; an obscure saying; an enigma; a parable. 

  • A drama exemplifying a proverb. 

  • A familiar illustration; a subject of contemptuous reference. 

verb
  • To name in, or as, a proverb. 

  • To write or utter proverbs. 

  • To provide with a proverb. 

watchword

noun
  • A word used as a motto, as expressive of a principle, belief, or rule of action; a rallying cry. 

  • A prearranged reply to the challenge of a sentry or a guard; a password or signal by which friends can be known from enemies. 

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