blacken vs blur

blacken

verb
  • To make dirty. 

  • To defame or sully. 

  • 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. 

blur

verb
  • To smear, stain or smudge. 

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

  • To become indistinct. 

  • To transfer the input focus away from. 

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

adj
  • In a state of doubt or confusion. 

noun
  • Something that appears hazy or indistinct 

  • A smear, smudge or blot 

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