seventh son of a seventh son

a reference to the belief that the seventh son of a seventh son was endowed with notable talent and supernatural powers. Seven was regarded as a sacred and magical number among many ancient peoples. According to a belief that persisted through the Middle Ages, the seventh son of a seventh son was endowed with the power of not only curing diseases and disorders of all kinds, but also of practicing magic and foreseeing future events. As late as the nineteenth century many people still believed that the seventh son of a seventh son was a born physician and possessed intuitive knowledge of the healing art. The natural gifts of such a person were supposed to be more effective in medicine than the professional training of an ordinary doctor.