Definition & Meaning of "[promise] {sb} the (moon|earth|world)"

What is the origin of the idiom "promise someone the moon" and when to use it?

The phrase "promise someone the moon" is an idiomatic expression that denotes making impractical promises or commitments to someone. The exact origin is not precisely documented, but it is rooted in the idea of offering something extremely grand or valuable, such as the moon, earth, or the entire world, as a pledge.