escarpment vs promontory

escarpment

noun
  • A steep descent or declivity; steep face or edge of a ridge; ground about a fortified place, cut away nearly vertically to prevent hostile approach. 

promontory

noun
  • A high point of land extending into a body of water, headland; cliff. 

  • A rounded elevation in the tympanum of the ear. 

  • A projection on the sacrum. 

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