why did they change dr. ivo. robotnik to eggman?

[supersonic200]

i have no idea so can you tell me what happen?

[Spirit Dragon]

Eggman was always his name, at least in Japan. Robotnik was just something to make it less ridiculous for the American crowd. They eventually decided they didn't need to do that anymore.Egg and man. A man that is/looks like an egg. It's a ridiculous name. But the japanese audience don't know the actual meaning/it's foreign so it sounds cook.
For english audience they just used the word 'robot' and made it a name.
But then later changed it back.

Yuji Naka has explained that "Robotnik" is the character's "real name" while "Eggman" is a "common name taken after his shape." Beginning with Sonic Adventure, Sega began referring to him more as Eggman in both languages, with the use of the name Robotnik becoming rare.

Though in Sonic Adventure 2 battle, Eggman's grandfather is Robotnik.

[TheGameNinja]

There's the answer. Try Wikipedia next time. Locked.