nonprofessional vs unskilled

nonprofessional

adj
  • not professional; amateur 

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

unskilled

adj
  • Of a person or workforce: not having a skill or technical training. 

  • Of a job: not requiring skill or training. 

  • Of a made object: inexpertly made or showing a lack of skill. 

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