"old shoe" 的定义和意义

What is the origin of the idiom "old shoe" and when to use it?

The idiom "old shoe" originated in the 18th century and is used to describe a person who is familiar, comfortable, or reliable. The phrase likens the familiarity and ease of an old, worn-in shoe to a person with whom one has a long-standing and comfortable relationship. It is used to convey a sense of trust and reliability in the person's character or behavior.