knap vs tump

knap

verb
  • To make a sound of snapping. 

  • To rap or strike sharply. 

  • To shape a brittle material having conchoidal fracture, usually a mineral (flint, obsidian, chert etc.), by breaking away flakes, often forming a sharp edge or point. 

noun
  • A protuberance; a swelling; a knob. 

  • A small hill 

  • A sharp blow or slap. 

  • The crest of a hill 

tump

verb
  • to bump, knock (usually used with "over", possibly a combination of "tip" and "dump") 

  • To form a mass of earth or a hillock around. 

  • To fall over. 

  • To draw or drag, as a deer or other animal after it has been killed. 

noun
  • A tumpline. 

  • A mound or hillock. 

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