Signore Pelizzoli claimed that the word has "no meaning", just a nickname...I've heard it said to mean "poker-face", but not buying that 100% (how popular is poker in Italy: clearly they play cardgames and gamble but do they even have such an expression?) and also that it's a bit more rude than that, but...the guy who has lived in Italy and speaks Italian fluently (Citoyen du Monde) once said he has no familiarity with Bergamo regional dialect or slang, which is apparently what the word "Ciöcc" is.
I can tell you that if you pronounce "chooch" in front of certain Central/South Americans (Columbians for sure) you'll be using a pretty dirty insult.