mattock vs woodchipper

mattock

noun
  • An agricultural tool whose blades are at right angles to the body, similar to a pickaxe. 

verb
  • To cut or dig with a mattock. 

woodchipper

noun
  • A machine for reducing wood to woodchips 

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