According to a Wii U accessory package, the code name for the Wii U Gamepad is WUP-010. Just like it's predecessors, being the Wii RVL(Revolution), DS NTR(Nitro), Gamecube DLP(Dolphin) and others, this would mean that the true code name would derive from "WUP". My immediate assumption would be "Wii U Project" and not "Profect Cafe"or "Cafe" only.
Here's the package I was talking about (the code is near the bottom):

This would also put an end to those spec rumors from vgleaks.com, since they were calling the DEV Kits, "CAT-DEV" and not "WUP-DEV":
http://www.vgleaks.com/wii-u-first-devkits-cat-dev-v1-v2-classic-controller-adapter/
What do you guys think?