What is when a guy says sleep tight?

When a guy says "sleep tight", it is a phrase used to bid someone goodnight and to wish them a restful, peaceful sleep. The phrase dates back to the 19th century when beds were made with ropes that needed to be tightened before being slept on. Saying "sleep tight" meant for the person to ensure that the ropes were tightened so that they would have a comfortable sleep. Nowadays, the phrase is used as a polite and caring way to say goodnight to someone. It can be used among any gender or age group to show affection or concern for their well-being.