knock back vs nonplus

knock back

verb
  • To stun; to surprise. 

  • To drink an alcoholic beverage swiftly or often. 

  • To press or knead (dough) so as to remove air bubbles. 

  • To reject; to refuse. 

nonplus

verb
  • To bewilder or perplex (someone); to confound, to flummox. 

noun
  • A state of bewilderment or perplexity. 

How often have the words knock back and nonplus occurred in a corpus of books? (source: Google Ngram Viewer )