Hi! The Urban Dictionary says “Chachi” is from the sitcom “Happy Days", http://www.urbandictionary.com/define.php?term=Chachi where there is a character named “Chachi Arcola”. I read about "Happy Days" at Wikipedia, http://en.wikipedia.org/wiki/Happy_Days and I did not see how this term “Chachi” is related to the character in Happy Days. Is it because the character “Chachi Arcola” is always over-fashionably dressed and acts as if he is very cool, smart and stylish in "Happy Days"? [I have never seen this show, just a guess.] Do you know why “Chachi” is used to describe someone who thinks he/she is a bit too cool? [Fringe] Peter: Sorry, Walter. Better luck next time. Astrid: Anyone ready for lunch? [Astrid walks into the lab and sees Peter standing there with the missing sleeves – Peter cut off his own sleeves with scissors during the hypnagogic trance.] [to Peter] What's up, Chachi?