1560, from L. insanus "mad, insane, outrageous, excessive, extravagant," from in- "not" + sanus (see sane). Originally only of persons; of actions, from 1842. Cf. lunatic; and It. pazzo "insane," originally a euphemism, from L. patiens "suffering."
Ger. verrückt, lit. pp. of verrücken "to displace," "applied to the brain as to a clock that is 'out of order' " [Buck].