"[pay] {sb} back in {one's} own (coin|crown)" 的定义和意义

What is the origin of the idiom "pay someone back in their own coin" and when to use it?

The origin of the idiom "pay someone back in their own coin" can be traced back to the idea of currency or payment. In the past, coins were used as a form of payment, and each coin had a specific value. When someone paid one with a coin, one received exactly what was owed to one. Similarly, when one "pays someone back in their own coin," one is figuratively giving them back the same kind of treatment or behavior they have given one. It is typically used in situations where someone wants to retaliate or respond to another person's actions, words, or behavior by using similar tactics or treatment that they have received.