Definition & Meaning of "[turn] up like a bad penny"

What is the origin of the idiom "turn up like a bad penny" and when to use it?

The phrase "turn up like a bad penny" is an idiomatic expression that originated in the 18th century. It refers to someone or something that keeps reappearing, often when they are unwelcome or unwanted. The "bad penny" in the phrase alludes to a counterfeit or defective coin, which nobody wants. So, when someone or something "turns up like a bad penny," it means they keep showing up even when they are not wanted or expected.