fossick vs track down

fossick

verb
  • To search for something; to rummage. 

  • To search for gems, gold, etc., on the surface or in abandoned workings. 

  • To be troublesome. 

  • To elicit information; to ferret out. 

track down

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

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

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