knock for a loop vs set upon

knock for a loop

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

set upon

verb
  • To begin an activity; to embark upon a course of action. 

  • To attack someone. 

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