incoherence vs intelligibility

incoherence

noun
  • The quality of not making logical sense or of not being logically connected. 

  • Something incoherent; something that does not make logical sense or is not logically connected. 

  • Thinking or speech that is so disorganized that it is essentially inapprehensible to others. 

intelligibility

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

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

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