Lunatic
Middle English, lunatik,
Old French, lunatique,
Latin lnticus, lna, the moon
Latin, lunaticus, moonstruck, from luna moon
Originally, the tag of “lunatic” was applied to those who worshipped the Earth’s Moon -- in much the same manner as an extreme “fan” becomes a “fanatic”, and one who criticizes others becomes a critic. The word then evolved from the belief that intermittent insanity was caused by the phases of the Moon.