pay sb. back in sb's own coin 以牙还牙
【讲解】
该习语源于中世纪商业习俗。当时随着商业的发展,借贷也较为频繁。可是由于各国君王,甚至大主教和领主都有权发行货币,因此货币的种类繁多,面值混乱。为保险起见,债主在借款之初就申明要以同样的货币还款。现在 pay sb. in sb's own coin 转喻为“ 一报还一报”,意近汉语的“以其人之道还治其人之身”。
【对话】
A:John beat me black and blue yesterday.
A:约翰把我打得鼻青脸肿。
B:Why?
B:为什么?
A:Because I told the teacher about his cheating on the exam.
A:因为我告诉老师他考试作弊。
B:He goes too far.
B:他太过分了。
A:I'm determined to pay him back in his own coin.
A:我想以牙还牙。
B:You can never do that.
B:你千万别那么样。