proc is not a word that I believe is short for anything. Procing is the term
that I first encountered from verant's game designers to refer to the "act of a
weapon casting a spell on its target/wielder". The entomology of this word is
probably a suitable question for submission to "ASK milo". Word of advice:
spell his name right and loose any attitude you might have - he will rip you to
shreds otherwise (eheeheh).