No wonder that Chauvelin's spies had failed to detect, in the apparently brainless nincompoop, the man whose reckless daring and resourceful ingenuity had baffled the keenest French spies.
[ 'nin-k&m-"püp, 'ni[ng ] (noun.) 1676. Earlier (1676) nicompoop, possibly from Latin non compos mentis (“not of sound mind”), although the lack of the second n in the early form and the original meaning of “fop” cast doubt on this origin.