accessibility vs intelligibility

accessibility

noun
  • The quality of being accessible, or of admitting approach; receptiveness. 

  • Features that increase software usability for users with certain impairments. 

intelligibility

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

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

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