moon-calf

noun, plural moon·calves.

1. a congenitally grossly deformed and mentally defective person.
2. a foolish person.
3. a person who spends time idly daydreaming.

noun plural -calves (-ˌkɑːvz)

1. a born fool; dolt
2. a person who idles time away
3. obsolete a freak or monster

n.also mooncalf, “abortive, shapeless, fleshy mass,” 1560s, attributed to the influence of the moon; from moon (n.) + calf (n.). In later 16c., “deformed creature, monster.”