What does Proc mean in WoW Classic?
Proc is an abbreviation that refers to a weapon, item or ability activating with the “Chance on Hit” or “Chance on Use” effect (an ability or a spell).
Why is it called proc?
Proc was originally short for “spec_proc” (spec_proc is short for “special process”) which is a term used by the original programmer of Circle-MUD, Jeremy Elson. It might have been used by the original programmers of diku-MUD as well.