Short for spec_proc (special procedure), which is a bit of code triggered to cover a special case that the default code doesn’t handle.
In the older muds there was almost no variation between what a given object could do. For example all weapons used the weapon type, then you could specify damage type (was it a sword or a mace), damage ranges, and so on.

To get the weapon to do anything special, you had limited choices. Depending on the architecture, you could attach a spell to be cast, or could attach a script if the code supported it. In the codebases that Brad & co. played, the devs could not script, so the codebase allowed a pointer to a special hardcoded procedure to be entered in the weapon data.

“Proc” is almost entirely EQ slang… Even in the muds, it wasn’t that widely used because only some codebases used the term. It took EQ publicizing the inherited term to make it common knowledge.

대충 mud게임에서 쓰던 spec_proc 이라는 프로그래밍 용어 줄여서 proc이라고 부르는거