"Eggman" was a term coined by Sonic in Sonic Adventure (in Western translations). By Adventure 2, Robotnik eventually accepted that "Eggman" would forever be his name from that point onward.
As for the comics, I believe "Eggman" was actually the mind inside a character known as "Robo-Robotnik", according to the pre-Genesis Wave. It's been a long time since I've read that arc.
Officially he's always been named Dr. Eggman... in Japan. When Sonic was introduced to a western audience in the 90s he was renamed Dr. Robotnik in the manuals.
Eventually Sega passed ownership of Sonic from Japan to America and for the Dreamcast era bits of Sonic's lore has been rewritten to say that Dr. Robotnik is indeed his real name, as confirmed in Sonic Adventure and continues to be his family name in Sonic Adventure 2 as Gerald Robotnik is confirmed to be his grandfather. While in Sonic Adventure Robotnik silenced Sonic for calling him "Eggman" the names simply became his moniker, as well as calling his empire after the name.
Perhaps he is simply aware he simply resembles a large egg to argue against it.
Sacorguy79 wrote: "Eggman" was a term coined by Sonic in Sonic Adventure (in Western translations). By Adventure 2, Robotnik eventually accepted that "Eggman" would forever be his name from that point onward.
As for the comics, I believe "Eggman" was actually the mind inside a character known as "Robo-Robotnik", according to the pre-Genesis Wave. It's been a long time since I've read that arc.
It's actually the other way round. In Japan his name was Eggman and the western manuals renamed him Dr. Robotnik which stuck with cartoons and comics up to Sonic Adventure.