blur vs darken

blur

verb
  • To make indistinct or hazy, to obscure or dim. 

  • To cause imperfection of vision in; to dim; to darken. 

  • To become indistinct. 

  • To transfer the input focus away from. 

  • To smear, stain or smudge. 

adj
  • In a state of doubt or confusion. 

noun
  • Something that appears hazy or indistinct 

  • A smear, smudge or blot 

darken

verb
  • To cloud, obscure, or perplex; to render less clear or intelligible. 

  • To become gloomy, darker in mood. 

  • To render gloomy, darker in mood. 

  • To become dark or darker (having less light). 

  • To make dark or darker by reducing light. 

  • To make dark or darker in colour. 

  • To blind, impair the eyesight. 

  • To become dark or darker in colour. 

  • To be blinded, lose one’s eyesight. 

  • To make foul; to sully; to tarnish. 

  • To get dark (referring to the sky, either in the evening or as a result of cloud). 

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