boathook vs graplin

boathook

noun
  • A pole or rod with such a hook at one end. 

  • A hook attached to a pole used for pulling or pushing boats, rafts, logs or other objects to or from the side of a boat. 

graplin

noun
  • A grapnel (small anchor). 

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