Free from a difficult situation.
To be in a difficult situation is like hanging "on" a "
hook"; to get free of the problem you
must get "off the
hook".
We've caught you again, but this time you won't get off the
hook so easily!" You are "off the
hook" when you are no longer responsible for some problematic situation. Example: "We found the guy who stole the
money, so we know you didn't do it; you're off the
hook." When you get yourself free from a difficult situation you are no longer "on the hook"; you are "off the hook." Example: "You're lucky; it turns out that Dad never heard you come in late last night." Answer: "Great, that means I'm off the hook!