blacken vs hebetate

blacken

verb
  • To defame or sully. 

  • To make dirty. 

  • To cook (meat or fish) by coating with pepper, etc., and quickly searing in a hot pan. 

  • To become black. 

  • To cause to be or become black. 

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 blacken and hebetate occurred in a corpus of books? (source: Google Ngram Viewer )