casern vs stockade

casern

noun
  • A lodging for soldiers in a garrison town (formerly usually near the rampart); a barracks. 

stockade

noun
  • a military prison 

  • an enclosure protected by a wall of wooden posts 

verb
  • To enclose in a stockade. 

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