casern vs dormitory

casern

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

dormitory

noun
  • A building or part of a building which houses students, soldiers, monks etc. who sleep there and use communal further facilities. 

  • A room containing a number of beds (and often some other furniture and/or utilities) for sleeping, often applied to student and backpacker accommodation of this kind. 

  • A dormitory town. 

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