knock over vs topple

knock over

verb
  • To bump or strike something in such a way as to tip it 

  • To rob; to stage a heist of. 

topple

verb
  • To push or throw over 

  • To overturn 

  • To overthrow something. 

  • To totter and fall, or to lean as if about to do so. 

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