sift out vs specify

sift out

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

specify

verb
  • To include in a specification. 

  • To state explicitly, or in detail, or as a condition. 

  • To bring about a specific result. 

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