Siso stands for "spicy in, spicy out". A phrase to help us remember that although spicy things taste good, they may also burn the hell out of your a-hole on the way out.
Person 1: What kind of wings should we get? Inferno?
Person 2: Siso, bro. You don't want an ass like a Japanese flag, do you?
Person 1: Good point, let's get teriyaki.