The word "lunatic" traditionally refers to a person who is considered to be mentally ill or insane. It often carries a connotation of eccentricity or erratic behavior, particularly in a way that is viewed as irrational or unpredictable. Historically, the term was linked to the moon ("luna" in Latin), based on the belief that changes in the moon could influence mental states.
The word "lunatic" comes from the Latin "lunaticus," which means "moonstruck" or "of the moon." This stems from the belief in ancient times that the moon had a direct effect on human behavior, particularly leading to episodes of madness or insanity.