postern vs subsidiary

postern

adj
  • Situated at the rear; posterior. 

noun
  • A back gate, back door, side entrance, or other gateway distinct from the main entrance. 

  • A subterranean passage communicating between the parade and the main ditch, or between the ditches and the interior of the outworks. 

subsidiary

adj
  • Secondary or subordinate. 

  • Of or relating to a subsidy. 

  • Auxiliary or supplemental. 

noun
  • A company owned by a parent company or a holding company, also called daughter company or sister company. 

  • A subordinate theme. 

  • One who aids or supplies; an assistant. 

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