Definition & Meaning of "[cry] for the moon"

What is the origin of the idiom "cry for the moon" and when to use it?

The phrase "cry for the moon" is an idiom that means to make an unreasonable or extravagant request or demand, often one that is unattainable or impractical. The origin of this expression can be traced back to the idea that crying for the moon, a celestial body out of reach, is akin to asking for something impossible.