casern vs harborage

casern

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

harborage

noun
  • A place for refuge for a vessel. 

  • A condition on land favorable to infestation by animals considered pests. 

  • A place of shelter or entertainment. 

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