dragnet vs ferret out

dragnet

verb
  • To make heightened efforts to catch a suspect. 

  • To drag a net across the bottom of a body of water. 

noun
  • Heightened efforts by law-enforcement personnel to capture suspects. 

  • A net dragged across the bottom of a body of water. 

ferret out

verb
  • To discover something after searching. 

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