Bosco is the ATM code of George Costanza, as seen in the episode The Secret Code. It is named after choclate sauce.
Story
George is unwilling to tell anyone his ATM code, even his fiance Susan, who tells him it is a sign of trust for him to tell her his code.
While looking after Mr. Peterman's mother, he falsely thinks she is unresponsive, and takes her to the hospital. George decides to tell someone his code, so he tells her. She wakes up saying bosco louder and louder and shortly after she does this, Peterman's mother dies. Peterman tries to find out what this means, but cannot figure it out. When George is with Peterman, they find a man who is trapped in the bank, which is almost on fire, and his sleeve is stuck in the ATM machine. In order to open the ATM up, Peteman begs George for his code, which he gives up, and the episode ends. Although speculation, it is probable that Peterman yelled at George for not saying that he told his mom bosco.