why is a moon carved into a bathroom or latrine?

back in medevil times, the moon was a source of light.

Logically, the moon would light the bathroom enough to see where to sit, and to see where to wipe. :p

My guess is ventalation - you need to get a little air flowing in, without allowing a lot of visibility of what you're doing - a crescent moon seems ideal for that

Dont know if thats right, but it seems logical

because when you show your bare butt its called mooning