Idiot, n.
Etymology: [F. idiot, L. idiota an uneducated, ignorant, ill- informed person, Gr. Idiom.]
1. A man in private station, as distinguished from one holding a public office. [Obs.] St. Austin affirmed that the plain places of Scripture are sufficient to all laics, and all idiots or private persons. Jer. Taylor.
2. An unlearned, ignorant, or simple person, as distinguished from the educated; an ignoramus. [Obs.] Christ was received of idiots, of the vulgar people, and of the simpler sort, while he was rejected, despised, and persecuted even to death by the high priests, lawyers, scribes, doctors, and rabbis. C. Blount.
3. A human being destitute of the ordinary intellectual powers, whether congenital, developmental, or accidental; commonly, a person without understanding from birth; a natural fool; a natural; an innocent. Life . . . is a tale Told by an idiot, full of sound and fury, Signifying nothing. Shak.
4. A fool; a simpleton; -- a term of reproach. Weenest thou make an idiot of our dame Chaucer.
Shades of meaning
Fernald lists idiot only as an antonym, under scholar.
He lists it without comment; the entries above explain its neighbors.