knock down vs reduce

knock down

verb
  • To reduce the price of. 

  • To drink fast. 

  • To disassemble for shipment. 

  • To hit or knock (something or someone), intentionally or accidentally, so that it falls. 

  • To demolish. 

  • To approve a drinking toast by banging glasses on the table. 

  • At an auction, to declare (something) sold with a blow from the gavel. 

reduce

verb
  • To bring down the size, quantity, quality, value or intensity of something; to diminish, to lower. 

  • To annul by legal means. 

  • To convert to written form. (Usage note: this verb almost always appears as "reduce to writing".) 

  • To lose weight. 

  • To perform a reduction; to restore a fracture or dislocation to the correct alignment. 

  • To bring to an inferior state or condition. 

  • To simplify an equation or formula without changing its value. 

  • To bring to an inferior rank; to degrade, to demote. 

  • To convert a syllogism to a clearer or simpler form. 

  • To add electrons / hydrogen or to remove oxygen. 

  • To humble; to conquer; to subdue; to capture. 

  • To strike off the payroll. 

  • To decrease the liquid content of food by boiling much of its water off. 

  • To produce metal from ore by removing nonmetallic elements in a smelter. 

  • To express the solution of a problem in terms of another (known) algorithm. 

  • To reform a line or column from (a square). 

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