harpoon vs hunting knife

harpoon

noun
  • A spearlike weapon with a barbed head used in hunting whales and large fish. 

  • A harmonica. 

verb
  • To shoot something with a harpoon. 

hunting knife

noun
  • A large knife designed for use in hunting animals, usually with a smooth front edge and a back edge that is partially serrated for sawing. 

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