pocketknife vs puukko

pocketknife

noun
  • A knife with blades or tools that the user can fold or retract into its handle, and of a size small enough for carrying safely and handily in a pocket, especially when suited to heavier duty uses or ad hoc applications outdoors or in workshops. 

puukko

noun
  • A type of sharp, pointed knife of Nordic heritage, with a short blade and flat back; normally worn in a sheath on the waist, and used for woodcrafts and as hunting knife. 

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