dunderhead

noun

1. (dated)A stupid person; a dunce.

   “You're the stupidest dunderhead I ever saw or ever heard of, so help me Moses!”

   “Poor old fellow's a dunderhead. That's where it is in a nutshell. Never could make a living. […] Nice old chap as ever lived. Only impractical, dreamy. Gentle as a sheep—and no more capable of running that big, expensive plant than a motherly old ewe.”

   “Cheney & Company swooned over Mr. Chalabi because he was telling them what they wanted to hear. . . . A half-dozen dunderheads who thought they knew everything assumed they could control Mr. Chalabi and use him as the instrument of their utopian fantasies.”