accessibility vs perspicuousness

accessibility

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

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

perspicuousness

noun
  • The state or characteristic of being perspicuous; perspicuity. 

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