sleep tight
The phrase "sleep tight" is an idiomatic expression that is commonly used to wish someone a restful and peaceful sleep. It originated from the practice of tightening the ropes or straps of a bed frame or mattress to ensure that it is sturdy and secure before going to sleep. Thus, the phrase encourages the person to sleep in a comfortable and secure manner.
An idiom is a phrase or expression that usually presents a figurative, non-literal meaning attached to the phrase. Does that sound fun? It can be!
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