intelligibility vs obscurity

intelligibility

noun
  • The quality of recorded speech of every word being understandable. 

  • That which is intelligible; the degree to which something is intelligible. 

obscurity

noun
  • The state of being unknown; a thing that is unknown. 

  • The quality of being difficult to understand; a thing that is difficult to understand. 

  • Darkness; the absence of light. 

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