carceral vs penitentiary

carceral

adj
  • Of or pertaining to imprisonment or a prison. 

penitentiary

adj
  • Of or relating to the punishment of criminals. 

  • Of or relating to penance; penitential. 

noun
  • A state or federal prison for convicted felons; (broadly) a prison. 

  • A priest in the Roman Catholic Church who administers the sacrament of penance. 

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