What is the origin of the idiom "for old times' sake" and when to use it?

The origin of the idiom "for old times' sake" is rooted in the idea of nostalgia and the feelings derived from it. This phrase implies doing something or revisiting a place, person, or experience from the past to evoke fond memories or reconnect with the past. It likely originated as a way to cherish and honor the memories of earlier, perhaps simpler or happier, times. This expression is now used when someone wants to do something or engage in an activity that they used to do in the past, often as a way to reminisce or revive positive memories associated with that activity or time period. It is often used in a friendly or emotional context.