As for Coruscant, it is first mentioned in the book Heir to the Empire by Timothy Zahn. At the time I always thought he'd invented it and not Lucas (his description of it is somewhat different than it appears in the prequels, also, as is Kashyyyk). That is from 1991, so of course many people already knew about it when the SE came around. Gah, I love the Thrawn trilogy--it's more 'canon' to me than the prequels ever have been.
As for Coruscant, it is first mentioned in the book Heir to the Empire by Timothy Zahn. At the time I always thought he'd invented it and not Lucas (his description of it is somewhat different than it appears in the prequels, also, as is Kashyyyk). That is from 1991, so of course many people already knew about it when the SE came around. Gah, I love the Thrawn trilogy--it's more 'canon' to me than the prequels ever have been.