I don't know. The "4" letter word was a spoiler clue given to readers by Kristen at eonline. Not the most reliable source, but is usually pretty solid with these type of clues. They just don't always end up being what you think they should be.
The very phrase, "The Island is (a) _ _ _ _" is open to many interpretations.
The 4-letter word could be a name like "Elba" in which case the answer could be anything and not important to the overall questions since name of the island might have very little, if any meaning. I mean maby Jacob named the Island "Orst" for some reason way back when. It would be an interesting fact, but would really mean nothing to the viewers.
On the other hand if the answer is "Lock", "Door", or something like that then it might give us some insight in to what's going on.