prefer vs sift out

prefer

verb
  • To present or submit (something) to an authority (now usually in "to prefer charges"). 

  • To be in the habit of choosing something rather than something else; to favor; to like better. 

sift out

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

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