dullen vs uneven

dullen

verb
  • To become dull or duller; to dull. 

  • To make dull or duller; to dull. 

uneven

verb
  • To make uneven. 

adj
  • Not even 

  • Not uniform 

  • Varying in quality 

  • Odd 

  • Not level or smooth 

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