It's not used in any of the films, but I believe the novelization of Star Wars calls him Palpatine.Anchorhead said:
Character question for the more versed, if I may.
When did the name Palpatine first show up? I see it's in the Zahn novels and I was wondering if it's another contribution of his, the way Coruscant is. I don't remember it in Return, but I'm not very familiar with that film.
*walks over to new bookshelf in the living room*
Yes, right here on the first page of the prologue. "Senator Palpatine"