Idiot originally meant a person that was not interested in participating in politics (antique Greek, see Athenian democracy).
In ancient Athens, an idiot was a person who declined to take part in public life, such as democratic city government. Since such activities were honorable and could directly affect all citizens, idiot was a term of derision.
The word comes from the Greek word ιδιωτης, idiôtês, "a private citizen, individual", from ιδιος, idios, "private".
Another use for Idiot is as a medical term used to describe a person, such as Hadal, with a form of mental retardation or a very low IQ level.
Idiot is also a derogatory term used by one person to insult another. Although it is an insult it is often not deemed to be vey offensive and is sometimes used between friends in an unaggrresive manner.
An example of the word's use is as follows:-
"Dave, You know that homework you leant me?"
"Yes."
"Well, I kind of lost it."
"You Idiot!"
See also idiotism.