Where did the saying speak of the devil come from?

The saying "speak of the devil" originates from the longer phrase "speak of the devil and he shall appear," which dates back to at least the 16th century. It suggests that mentioning someone—often in a negative context—can lead to their unexpected appearance. Over time, it has evolved into a more light-hearted expression used when someone arrives just as they are being talked about. The phrase reflects the belief that invoking the devil by name could summon him, a superstition common in various cultures.