curly bracket vs round bracket

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. 

round bracket

noun
  • Each of the signs ( and ); parenthesis, bracket (in a strict sense). 

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