Clearly, such is a title earned. Bowing to its English birth, one might be tempted to look to the usage of the title esquire there. However, the voyage across the pond has affected more than one title in a peculiar manner. For example, in Victorian England, the medical profession was divided into physicians, who treated internal injuries by prescribing drugs, and surgeons, who dealt with broken bones. Smith said as an earned title, the lack of its use by attorneys is more of custom than propriety.
Doctor is derived from the Latin word for teacher.
Smith traces the first doctor's degree awarded to Bologna, Italy, at the end of the 12th century. Interestingly, this doctorate, from which all others flow, was in civil law. The Encyclopedia Britannica is Smith's authority for the fact that it was not until later that a doctorate in medicine followed. The only exceptions are in academic settings, or when in countries where attorneys are referred to as doctor. Opinion 321 came about as the entry degree for the practice of law changed from an LL.B., which required no undergraduate degree, to a J.D., which required a four-year baccalaureate.