blur vs umbra

blur

noun
  • Something that appears hazy or indistinct 

  • A smear, smudge or blot 

adj
  • In a state of doubt or confusion. 

verb
  • 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. 

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

umbra

noun
  • The fully shaded inner region of a shadow cast by an opaque object. 

  • The area on the earth or moon experiencing the total phase of an eclipse. 

  • The central region of a sunspot. 

  • One of the family Umbridae of mudminnows. 

  • A shadow. 

  • A sciaenoid fish, the umbrine. 

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