When I first started, You definitely didn't use 'DD' to mean 'DPS'. DD stood for Direct Damage, as in, a Wizard casting a spell that does a burst of damage in one go, not over time. If a spell caused Damage Over Time, it was a DOT. People weren't even counting their damage per second when I first started playing EverQuest back when there was only 1 expansion. At least, not to such a widespread degree like today. I hear people mention 'DD' in forums to this day, particularly in discussions about the actual terminology like this thread is, but I've only ever heard it used in-game back when I was starting out in EverQuest. (way before FFXI or WoW)