knock back vs turn down

knock back

verb
  • To reject; to refuse. 

  • To drink an alcoholic beverage swiftly or often. 

  • To stun; to surprise. 

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

turn down

verb
  • To refuse, decline, or deny. 

  • To reduce the power, etc. of something by means of a control, such as the volume, heat, or light. 

  • To reposition by turning, flipping, etc. in a downward direction; to double or fold down. 

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