The old school use of 'off the hook' is to "get away with something", or "not be responsible for something", i.e., the fish that got away was 'off the hook'.
Off the hook is actually a modernization of a series of slang words. Closely related to off the chain, there refering to something being so "fresh" and "new" that its literally right off the store shelf. (started in reference to clothes, the hangar being the hook)
A synomym for "busy". Taken from a phone reference; when you leave a phone off the hook, you get a "busy" signal. The phrase is used to convey that there were a lot of people attending a particular event.
or
"Don't get cooked, stay off the hook" lolololololol
By Frannie
Off The Hook
adj.
1. Freed, as from blame or a vexatious obligation: let me off the hook with a mild reprimand.
2. The Shiznit, something noteworthy, outstanding
3. Off the chain