dictum vs underword

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. 

underword

noun
  • A word placed below another, either literally or metaphorically: a subtext; an inadequate or subordinate term or description; a secret word or phrase; a watchword 

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