No, not the duck sound. I've been thinking about some of the doctors I've known. There was the anesthesiologist who was so bored by her job she would take business phone calls while in the operating theater. Then there was an orthopedic surgeon who got to be head of his department, not through skill but by being a royal SOB. He maintained an excellent record by blaming the patients for all of his screw-ups. They were just hypochondriacs.
Quack (n) - Medical charlatan. Dates from the 17th century from the Dutch word, kwaksalver, meaning seller of salves.