1) Ass 1) Cousin of Simple Simon 2) Simpleton 
A mooncalf (or moon-calf) is the abortive fetus of a cow or other farm animal. The term was occasionally applied to an abortive human fetus. The term derives from the formerly widespread superstition, present in many European folk traditions, that such malformed creatures were the product of the sinister influence of the Moon on fetal development....
the worst insult a commander can give to a lower-ranking soldier, meaning both idiot and coward
false conception or fleshy mass in the womb
• (n.) A monster; a false conception; a mass of fleshy matter, generated in the uterus. • (n.) A dolt; a stupid fellow.
Moon'calf` noun 1. A monster; a false conception; a mass of fleshy matter, generated in the uterus. 2. A dolt; a stupid fellow. Dryden. 
a congenitally grossly deformed and mentally defective person. · a foolish person. · a person who spends time idly daydreaming.