Truthsharer: Corn is actually more interesting. It’s because Koren in olde English meant grain and was a word interchangeably used with wheat. Thus, do to concerns for confusion B’nei Ashkenaz added corn to the list of things that aren’t Kitniyos.
(And now to be called an Apikores again: R’ Moshe has a famous T’shuvah where he explains why corn is Kitniyos but potatoes aren’t. He says because they had corn before the Minhag developed but they didn’t have potatoes because it was a New World vegetable. This, of course, is not quite true. Both corn and potatoes are New World crops. The difference is the name.)