intelligible vs middlebrow

intelligible

adj
  • Capable of being understood; clear to the mind. 

middlebrow

noun
  • A person or thing that is neither highbrow nor lowbrow, but in between. 

adj
  • Neither highbrow or lowbrow, but somewhere in between. 

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