1
general::
Phrase(s): *off the hook
Fig. freed from an obligation. (Alludes to a fish freeing itself from a fishhook. *Typically: be ~; get ~; get someone ~; let someone ~.) • Thanks for getting me off the hook. I didn’t want to attend that meeting. • I couldn’t get myself off the hook no matter what I tried.
McGrawhill's American Idioms And Phrasal Verbs
2
general::
Also, get or let off the hook. Released (or be released) from blame or annoying obligation, as in He was out of town during the robbery so he was off the hook, or I don't know how the muggers got off the book, or Once they found the real culprit, they let Mary off the hook. This idiom alludes to the fish that manages to free itself from the angler's hook and get away. [Mid-1800s]
American Heritage Idioms