History of the word idiot
Today's meaning: "A foolish or senseless person". Mentally deficient.
From Greek adjective idios, meaning "One's own or private", essentially "his own man". Noun form idiotes means "private person".
The meaning was simply a person who was not in the public eye, who held no public office. Common man. Since historically common people were not educated, a natural extension of this word became 'ignorant person'.
The word was borrowed from Greek, into Latin, as idiota. Then was borrowed into French as idiote, which later was borrowed into English.
