dull vs soften

dull

verb
  • To soften, moderate or blunt; to make dull, stupid, or sluggish; to stupefy. 

  • To render dull; to remove or blunt an edge or something that was sharp. 

  • To lose a sharp edge; to become dull. 

  • To render dim or obscure; to sully; to tarnish. 

adj
  • Not bright or intelligent; stupid; having slow understanding. 

  • Insensible; unfeeling. 

  • Not intense; felt indistinctly or only slightly. 

  • Sluggish, listless. 

  • Boring; not exciting or interesting. 

  • Not shiny; having a matte finish or no particular luster or brightness. 

  • Lacking the ability to cut easily; not sharp. 

  • Cloudy, overcast. 

  • Heavy; lifeless; inert. 

  • Not clear, muffled. 

soften

verb
  • To become soft or softer 

  • To make something soft or softer. 

  • To palatalize. 

  • To become or make (a consonant) more lenis, to lenite. 

  • To make less harsh 

  • To undermine the morale of someone (often soften up). 

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