Electonic Data Processing -- the people who were doing 'IT' before it was cool. We're talking 0ld sk00l here. The PDPs, the S/3x's and the Rand's.
It's been renamed an insane number of times as the world has progressed, from EDP, to just DP, to MIS, then IS and now it is just IT.
Remeber, there is no substance to the rumour that it will next be renamed to "Super Hightech Information Technology".