parole vs watchword

parole

noun
  • A word of honor, especially given by a prisoner of war, to not engage in combat if released. 

  • Originally, one's oath or word of honour, given as a condition of release from custody; now specifically, describing the release of a former prisoner under certain conditions, especially the promise of good behaviour. 

  • Language in use, as opposed to language as a system. 

  • The permission for a foreigner who does not meet the technical requirements for a visa to be allowed to enter the U.S. on humanitarian grounds. 

  • Conditional release of a prisoner (now especially before the end of a custodial sentence), or the term or state of such release; the system governing such releases. 

verb
  • To release (a prisoner) on the understanding that s/he checks in regularly and obeys the law. 

watchword

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

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

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