curly bracket vs paper fastener

curly bracket

noun
  • Either of the two characters { and }, i.e., left curly bracket { and right curly bracket }, with the shape of a curved, pointed line, having various uses in math, music, computer programming and chemistry. 

paper fastener

noun
  • A stationery fastening device made of thin, soft metal, with a round head and a flat, split shank, which is spread after insertion in a hole in a stack of pages, in much the same way as a cotter pin or a split rivet. 

  • Any similar stationery fastening device. 

How often have the words curly bracket and paper fastener occurred in a corpus of books? (source: Google Ngram Viewer )