Webster’s Revised Unabridged Dictionary · 1913
Idiocy
Id′i·o·cy (ĭd′ĭ·ō·sy̆), n. [From idiot; cf. Gr. ἐδιωτεία uncouthness, want of education, fr. ἰδιώτης. See Idiot, and cf. Idiotcy.] The condition or quality of being an idiot; absence, or marked deficiency, of sense and intelligence.
I will undertake to convict a man of idiocy, if he can not see the proof that three angles of a triangle are equal to two right angles. F. W. Robertson.