dictum vs watchword

dictum

noun
  • An authoritative statement; a dogmatic saying; a maxim, an apothegm. 

  • The report of a judgment made by one of the judges who has given it. 

  • An arbitrament or award. 

  • A judicial opinion expressed by judges on points that do not necessarily arise in the case, and are not involved in it. 

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 dictum and watchword occurred in a corpus of books? (source: Google Ngram Viewer )