insanity /in-sanˈi-ti/ noun

1. Lack of sanity
2. A degree of mental illness causing one to act against the social or legal demands of society or in which one is held to be not responsible for one's actions under law
3. Madness
4. Extreme stupidity

insane root noun (Shakespeare)

Prob a root mentioned by Plutarch, Life of Antony, perh hemlock, henbane or belladonna