root about vs shake down

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. 

shake down

verb
  • To search exhaustively. 

  • To shake someone so money falls from their pockets. 

  • To cause something to fall down by shaking it, or something it is attached to. 

  • To extort money from (someone) by means of threats. 

  • To subject something to a shakedown test. 

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