curly bracket vs paren

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. 

paren

noun
  • A parenthesis (bracket used to enclose parenthetical material in text). 

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