Wild, Chaotic, Unencumbered. Derived from ancient naval slang. The hook referred to the anchor. In violent storms, if the anchor would break loose from the seabottom (or break loose from the anchor chain - ref "Off the chain.."), the ship would be uncontrolled, free and wild. Utter chaos. Can you imagine anything more wild than a uncontrolled ship in a hurricane?
That party was OFF THE HOOK!