discard vs sift out

discard

verb
  • To throw away, to reject. 

  • To make a discard; to throw out a card. 

  • To dismiss from employment, confidence, or favour; to discharge. 

noun
  • A temporary variable used to receive a value of no importance and unable to be read later. 

  • Anything discarded. 

  • A discarded playing card in a card game. 

sift out

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

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