nunchaku vs singlestick

nunchaku

noun
  • The skill of using this weapon in martial arts. 

  • A weapon originating from Okinawa, Japan, consisting of two sticks joined by a chain or cord. 

singlestick

noun
  • A martial art, sport or exercise using a cudgel or backsword. 

  • A one-handed wooden stick used for fencing in place of a sword. 

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