A "Promise" is an insult or a nickname for someone or something who has done something wrong / is the worst, an insult for everything. Not too rude, not too kind.
You can use the word "Promise" for anything, anyone, no matter what they have done, it is the best insult.
Dave: Hey man, did you like that twilight movie
Greg: Fuck you, Promise.
Dave: Sorry for stealing your girlfriend.
Greg: Fucking Promise.
Dave: Hey man, you no that Jim kid?
Greg: Yeah bro, he's a fucking promise hey.