cavity vs exedra

cavity

noun
  • A hollow area within the body. 

  • A hole or hollow depression in a solid object. 

  • A small or large hole in a tooth caused by caries; often also a soft area adjacent to the hole also affected by caries. 

exedra

noun
  • A semicircular recess, with stone benches, used as a place for discussion. 

  • A curved bench with a high back. 

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