What's the difference between mind flayers and illithids?

[Bootlebat]

I always figured mind flayer was a slang term an illithid is the proper name.

 

[Olive]

I think Mind Flyer was the original name and illithid was the 2e name (where they changed a lot of monster names).

 

[Paul Farquhar]

None.

Mind Flayer was the original name in the 1st edition Monster Manual. When the lore about them was expanded in the Dragon magazine, Illithid was invented as thier name for themselves (Mind Flayer being what others called them). This was fully incorporated into he core rules by 2nd edition.