exhaust vs knock out

exhaust

verb
  • To use up; to deplete, drain or expend wholly, or until the supply comes to an end 

  • To empty by drawing or letting out the contents 

  • To bring out or develop completely 

  • To discuss thoroughly or completely 

  • To subject to the action of various solvents in order to remove all soluble substances or extractives 

  • To draw or let out wholly; to drain off completely (:liquid) 

  • to tire out; to wear out; to cause to be without any energy 

noun
  • An exhaust pipe, especially on a motor vehicle. 

  • A system consisting of the parts of an engine through which burned gases or steam are discharged; see also exhaust system. 

  • The steam let out of a cylinder after it has done its work there. 

  • The dirty air let out of a room through a register or pipe provided for the purpose. 

  • exhaust gas. 

knock out

verb
  • To exhaust. 

  • To fall asleep, especially suddenly. 

  • To lose the scent of hounds in fox-hunting. 

  • To eliminate from a contest or similar. 

  • To put to sleep. 

  • To complete, especially in haste; knock off. 

  • To render unconscious, as by a blow to the head. 

  • To strike or bump (someone or something) out. 

  • To cause a mechanism to become non-functional by damaging or destroying it. 

  • To communicate (a message) by knocking. 

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