hook是钩子的意思，off the hook也就是脱钩了，引申出的含义为“摆脱困境；脱身”。

【例句】
This time there was no one around to get him off the hook. 这一次，没有人能帮他脱离困境。

If you are caught coming in late again, you won't get off the hook so easily anymore.
如果我们再发现你晚回来，绝不会轻易放过你！