Idioms of moon in English

ask, cry, etc. for the moon

(informal) to ask for something that is difficult or impossible to get or achieve

Wanting a decent job and a home is hardly asking for the moon.

many moons ago

(literary) a very long time ago

All that happened many moons ago.

once in a blue moon

(informal) very rarely

over the moon

(informal, especially British English) extremely happy and excited

They’re over the moon about their trip to Japan.

promise (somebody) the earth/moon/world

(informal) to make promises that will be impossible to keep

Politicians promise the earth before an election, but things are different afterwards.

promise (somebody) the moon/earth/world

(informal) to make promises that will be impossible to keep

Politicians promise the moon before an election, but things are different afterwards.