However, the word mob meaning a group of people pre-dates all on-line games and even on-line it's self.
The other meaning of mob is organized crime, which is not an acronym. If it is, I don't know it.
Many mmorpg terms are strangely distorted or came to mean something different than what the word originally meant:
Add(original): To increase in number.
"Adds"(HATE THIS USE OF IT BECAUSE IT SOUNDS STUPID!) in mmorpg: Reinforcements, Backup, ambush, summoned, built enemy ect. This term imo needs to die, it's not specific enough by any means. Probably 10 year olds screwed this one up since they didn't know the proper definitions for extra badguys. Yes, I dispise this use of the word THAT much.
Mob(Original): The mass of people who are generally unthinking, or mass of badguys with no cohesion, proper formation or ability to think.
Mob(MMO): Enemy npc, Mobs for enemy npc's, which is silly, as mob was plural in general. I suspect 10 year olds screwed the term up to, when they heard older players refering to large groups of npc's as mobs since they probably just mashed together, got stuck on each other, tended to try and chase players up impassable terrain and clumped together like the AI does in Totally accurate battle simulator.
Noob: Short for newbie, but slowly came to mean "idiot who refused to learn how to play better".
Scrub(Original): Doctor in training(really).
Scrub(Sirlin, and my usual definition): Jerk who hates how other people play, also tends to be unable to improve at the game due to his construct of artificial rules. Can sometimes be a good player, or even a top player, but will become obsolete and irrelevant, and gives gamers a bad reputation.
Scrub(distorted): Noob, usually the scrubs use of the word scrub, ironicly.
Elite: Someone awesome at the job or combat role, often the best of the best. It's originally meant to be a good thing to be.
Elitist(Common, these days): Jerk who hoards all the money and doesn't pay his subordinates.
Elitist(Gamer): Jerk who hates others for how they play but is extremely good at the game and regularly changes to newer tactics when old ones are obsoleted. Has a tendency to give good gamers who enjoy playing competitively and even get paid for it a bad reputation(See, for example, Idra of SC2 before he quit). Can overlap with Scrub(Sirlin).
Just some examples of how the definition of some terms change for gamers.