patency vs perspicuity

patency

noun
  • Obviousness; clarity. 

  • The condition or state of being patent. 

  • The degree of openness (of a tube, such as a blood vessel or catheter); the relative absence of blockage or obstruction. Measured in percent. 

perspicuity

noun
  • Clarity, lucidity, especially in expression; the state or characteristic of being perspicuous. 

  • Transparency; translucence. 

  • Perspicacity; insight. 

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