sift out vs winnow

sift out

verb
  • To isolate or identify one particular thing from a collection that includes less relevant things. 

winnow

verb
  • To separate, sift, analyse, or test by separating items having different values. 

  • To blow upon or toss about by blowing; to set in motion as with a fan or wings. 

  • To subject (granular material, especially food grain) to a current of air separating heavier and lighter components, as grain from chaff. 

noun
  • That which winnows or which is used in winnowing; a contrivance for fanning or winnowing grain. 

  • The act of winnowing 

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