^^^ Lock might be interesting, based on the double-meaning it would hold in this particular show.
Jack: What is the Island? TELL ME! I want ANSWERS! <throws a coconut that shatters against a palm tree>
Richard: One word - "Lock".
Jack: Locke? Locke's dead.
Richard: Lock is Locke and Locke is the Island.
<queue dramatic music and fade to commercial as Jack picks up another coconut>
Based on some of the other cryptic stuff that's been thrown around, answering questions without really
answering them, this kind of thing would fit right in.
I do like "cork", though. Makes perfect sense.