By the second season, the writers had the robot refer to himself as "A General Utility Non-Theorizing Environmental Control Robot" whenever the robot was required to explain what sort of robot he was.

In the third-season episode "Time Merchant," the art department decided to create a sign for the crate in which the robot was originally supposed to be shipped.

One of the art directors must have thought that with a few minor changes and omissions, he could transform "A General Utility Non-Theorizing Environmental Control Robot" into a memorable acyronym. The result is this:

ONE
General
Utility
Non
Theorizing
Environmental
ROBOT

Leaving out the word "control," the art director came up with the acronym "GUNTER." Thankfully, this horrible attempt at giving a name to the perpetually nameless robot failed and never caught on among the actors or crew.

Other failed names for the robot were Blinky (given by designer Robert K. Kinoshita because of the robot's blinking lights), Stu (modestly given by the robot's builder Bob Stewart), Junior (given to him by the crew on the set), and  Claude (given by Jonathan Harris as a pun on "Clawed," as in, a creature with claws).