promontory vs serration

promontory

noun
  • A rounded elevation in the tympanum of the ear. 

  • A projection on the sacrum. 

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

serration

noun
  • A set of teeth or notches. 

  • One of the teeth in a serrated or serrate edge. 

  • The state of being serrated. 

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