"have one's number"的定义和意义

What is the origin of the idiom "have one's number" and when to use it?

The origin of the idiom "have one's number" is derived from the idea that everyone has a unique telephone number. In the context of this phrase, it means having someone figured out or knowing their true nature or intentions. This expression is used to convey that someone understands another person very well, often implying that they can predict their behavior or motives.