flush out vs track down

flush out

verb
  • Used other than figuratively or idiomatically: see flush, out. 

  • To drive out or expose something or someone, as a game bird or other game animal from cover. 

  • To flesh out. 

track down

verb
  • Used other than figuratively or idiomatically: see track, down. 

  • To hunt for or locate; to search for; to find. 

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