brass knuckles vs singlestick

brass knuckles

noun
  • A weapon consisting of a metal reinforcement for the clenched fist, with finger holes molded in. 

singlestick

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

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

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