blindside vs knock back

blindside

verb
  • To catch off guard; to take by surprise. 

  • To attack (a person) on his or her blind side. 

noun
  • The blindside flanker, a position in rugby union, usually number 6. 

  • A person's weak point. 

  • A tram/train driver's field of blindness around a tram (trolley/streetcar) or a train; the side areas behind the tram/train driver. 

  • The space on the side of the pitch with the shorter distance between the breakdown/set piece and the touchline; compare openside. 

  • A driver's field of blindness around an automobile; the side areas behind the driver. 

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. 

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