blur vs lighten

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. 

noun
  • Something that appears hazy or indistinct 

  • A smear, smudge or blot 

adj
  • In a state of doubt or confusion. 

lighten

verb
  • To make brighter or clearer; to illuminate. 

  • To become light or lighter in weight. 

  • To become brighter or clearer; to brighten. 

  • To make less serious or more cheerful. 

  • To illuminate with knowledge; to enlighten. 

  • To descend; to light. 

  • To emit or disclose in, or as if in, lightning; to flash out, like lightning. 

  • To alleviate; to reduce the burden of. 

  • To become less serious or more cheerful. 

  • To make light or lighter in weight. 

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