ferret out vs root about

ferret out

verb
  • To discover something after searching. 

root about

verb
  • To search for something in a similar manner. 

  • To rummage; to look for something in a somewhat aimless fashion. 

  • To forage by poking the snout here and there. 

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