track down vs underseek

track down

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

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

underseek

verb
  • To examine; explore; investigate. 

  • To spend too little time or effort in seeking. 

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