The universities had given the title of doctor of medicine for centuries. But these were few in number and many other competent people practiced medicine, as well as many quacks. The nineteenth century was the time when the use of the title ‘doctor’ became more regulation and the qualifications of doctors became more settled. This helped to set standards of competence and to make quacks more obvious.
If it walked like a duck, talked like a duck and looked like a duck... Before 1803 it may have been a quack.