cordillera vs crag

cordillera

noun
  • An extensive, continent-wide chain of mountains, especially one in the Americas. 

crag

noun
  • A rocky outcrop; a rugged steep cliff or rock. 

  • A rough, broken fragment of rock. 

  • A partially compacted bed of gravel mixed with shells, of the Pliocene to Pleistocene epochs. 

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