I just googled...

"Idiot" was originally created to refer to "layman, person lacking professional skill", "person so mentally deficient as to be incapable of ordinary reasoning".[6][7] Declining to take part in public life, such as democratic government of the polis (city state), such as the Athenian democracy, was considered dishonorable. "Idiots" were seen as having bad judgment in public and political matters. Over time, the term "idiot" shifted away from its original connotation of selfishness and came to refer to individuals with overall bad judgment–individuals who are "stupid". In modern English usage, the terms "idiot" and "idiocy" describe an extreme folly or stupidity, and its symptoms (foolish or stupid utterance or deed). In psychology, it is a historical term for the state or condition now called profound mental retardation.[8]