middlebrow vs nonprofessional

middlebrow

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

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

nonprofessional

noun
  • One who is not a professional; an amateur. 

adj
  • not professional; amateur 

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