knock down vs tumble

knock down

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

  • To drink fast. 

  • To disassemble for shipment. 

  • To reduce the price of. 

  • 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. 

tumble

verb
  • To fall end over end; to roll over and over. 

  • To smoothe and polish, e.g., gemstones or pebbles, by means of a rotating tumbler. 

  • To muss, to make disorderly; to tousle or rumple. 

  • To obscure the audit trail of funds by means of a tumbler. 

  • To perform gymnastics such as somersaults, rolls, and handsprings. 

  • To have sexual intercourse. 

  • To move or rush in a headlong or uncontrolled way. 

  • To drop rapidly. 

noun
  • A fall, especially end over end. 

  • An act of sexual intercourse. 

  • A disorderly heap. 

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