apartment vs boarding house

apartment

noun
  • A complete domicile occupying only part of a building, especially one for rent; a flat. 

  • A conceptual space used for separation in the threading architecture. Objects in one apartment cannot directly access those in another, but must use a proxy. 

boarding house

noun
  • A private house in which paying residents are provided with accommodation and meals. 

  • A boarding school building where boarders live during term time. 

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