Hi all, I have no formal education with electronics.. figured I would ask this question just because its bugging me and I need to know why.

Why are power planes named Vcc Vdd Vss etc... Do the two letters after the V mean anything in particular or is it just an arbitrary way of naming different power planes? At first I thought Vdd might have had something to do with Drain, Vss would have something to do with source how ever most of the schematics I have worked with have them the other way around... (Vdd is + and Vss is -)

Just curious.