The Sonic Team reveals why Dr. Robotnik's name was changed to Eggman
Turns out we were wrong all along...
Which came first, Dr. Robotnik or Eggman? We westerners have a certain affinity for the name Robotnik, but apparently, we've been wrong this whole time. Kind of. As it turns out, the character was never intended to have that name and was simply known as Eggman by the people who developed the game. The name Robotnik was brought about when the game was ported over to the west, and it seems the Developers never gave the green light to use that name.
In speaking with Game Informer, Sonic Team head, Takashi Iizuka answered many important questions, but the most intriguing of which had to do with the Dr. Robotnik/Eggman name.
"When the game was originally developed in Japan, they called the character Eggman. That was the name of the character, but when the game got localized and ported into the Sonic the Hedgehog that we know in the West, they decided to, without confirming with the development team, change his name to Ivo Robotnik or just Robotnik. That's kind of when everyone first learned about the character. Of course, this was without consulting the people who made the game. They just kind of went off and did it. It became super popular and everyone in the West kind of learned about the character as Robotnik. That went on through the "classic" series in the Genesis/Mega Drive era, but as far as the developers are concerned - the ones who made the character and the leaders of what this character is doing next - we really didn't want to have anyone in the universe with two names. To us, he's Eggman, but in the rest of the world he's called Robotnik. We wanted to unify that into one name moving forward. This is something I actually did in the Sonic Adventure series. I made it so that we understand the character's name is Robotnik, but his nickname is Eggman, and as far as everyone is concerned in the world now, we're just going to call him Eggman as his official name."
I'm glad to see that the Developers have (somewhat) embraced the Robotnik name, that said it is their game, and clearly they prefer Eggman. But to me (and probably many others), he will always be Dr. Robotnik.
Source: Game Informer