Douglas Harper's Etymology Dictionary
Wiktionary
dummkopf
n. A stupid person; a dolt, dimwit or blockhead
Usage examples of "dummkopf".
Early afternoon, day after I acted like a complete dummkopf and left the tent alone.
He cursed their teachers, their progenitors, and predicted a dim future for the human race if such dummkopfs were allowed anywhere near the practice of medicine.