dumb vs thickheaded

dumb

adj
  • Extremely stupid. 

  • Pointless, foolish, lacking intellectual content or value. 

  • Lacking brightness or clearness, as a colour. 

verb
  • To make stupid. 

  • To represent as stupid. 

  • To reduce the intellectual demands of. 

thickheaded

adj
  • stupid, obtuse or dumb. 

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