blur vs clear up

blur

verb
  • To become indistinct. 

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

  • To transfer the input focus away from. 

  • To smear, stain or smudge. 

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

noun
  • Something that appears hazy or indistinct 

  • A smear, smudge or blot 

adj
  • In a state of doubt or confusion. 

clear up

verb
  • To become free of certain blemishes. 

  • To depart or disappear. 

  • To clarify, to correct a misconception. 

  • To clean up. 

  • Of stormy weather, to dissipate, to become calm. 

  • To pot all of the remaining balls in a single turn. 

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