attrit vs knock out

attrit

verb
  • To engage in attrition; to quit or drop out. 

  • To be reduced in quantity through attrition. 

  • To lose, or to kill, troops by attrition due to sustained firepower. 

  • To wear down through attrition, especially mechanical attrition. 

noun
  • One who voluntarily or involuntarily leaves a company; a termed employee. 

knock out

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

  • 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 exhaust. 

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

  • To communicate (a message) by knocking. 

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