exertion vs usance

exertion

noun
  • An expenditure of physical or mental effort. 

usance

noun
  • Customary or habitual usage. 

  • Use. 

  • The interest paid on a borrowed sum, usury. 

  • The length of time permitted for the payment of a bill of exchange. 

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