chop down vs knock for a loop

chop down

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

  • To curtail, shorten 

knock for a loop

verb
  • To astonish; to stagger or overwhelm; to confuse or disorient. 

How often have the words chop down and knock for a loop occurred in a corpus of books? (source: Google Ngram Viewer )