dullen vs hebetate

dullen

verb
  • To make dull or duller; to dull. 

  • To become dull or duller; to dull. 

hebetate

verb
  • To render obtuse; to dull; to blunt. 

adj
  • obtuse; dull 

  • Having a dull or blunt and soft point 

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