I mean, a G/V-PU by any other name would smell just as sweet, wouldn't it?
Back in the old days we called 'em GP's--short for "graphics processors"--which worls for either 2d or 3d or both. I've always felt the "U" for "unit" was redundant and completely unnecessary, because whether it's a CP or GP that we're talking about, the "unit" part of the acronym is understood. If the chips weren't "units" they wouldn't exist, etc.
But putting a "U" on the end makes for some nifty marketing acronyms, of course, like CPU and GPU and VPU, and there you have it. Sort of makes them all sound more exotic to the layman, if you know what I mean.