enslave vs parole

enslave

verb
  • To make subservient; to strip one of freedom; enthrall. 

parole

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

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. 

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