Idiot. It's an easy word to pull out, and hurl when someone makes you mad. It'sthe nuclear option of insults, without having to descend into "Seven Little Words" territory. (Click that link. You're welcome.)
But I recently learned that the word "idiot" has a deeper and more nuanced meaning than just someone who maxes out the Stupid-O-Meter.®
An idiot in Athenian democracy was someone who was characterized by self-centeredness and concerned almost exclusively with private—as opposed to public—affairs. Idiocy was the natural state of ignorance into which all persons were born and its opposite, citizenship, was effected through formalized education. In Athenian democracy, idiots were born and citizens were made through education....
It's interesting to encounter this in the year 2016, as we have a very ripe selection of idiots (classical definition!) doing things like, deciding Trump isn't so bad because maybe Hillary took some lousy advice about an email server.