Hubertus was the oldest son of the Duke of Aquitaine, and he had a spiritual awakening while out hunting shortly after his wife died while giving birth to their son.
The story goes that, just as he was about to shoot a deer, the animal turned to Hubertus and lectured him that he should have more respect for animals. The deer is said to have told Hubertus that he should treat his quarry as if it had its own intrinsic value. It was the duty of the hunter to kill swiftly and to only shoot stags past their breeding age. A female stag with young in tow should never be shot.
After this miraculous turn of events, Hubertus became a priest and was made the first bishop of Liège, in Belgium, around 708 AD.
The story continues: shortly after he was made Bishop of Liège, Hubertus was visited by Saint Peter who gave him a "golden key" and told Hubertus that God had given him a special power against evil spirits.
A little while later, Hubert "miraculously" cured a man who had been bitten by a "rabid" dog after the "golden key" was heated red hot and plunged into the bite wound to cauterize it. I put "golden" in quotes here because gold does not get red hot -- it simply liquefies. The key was likely brass.
In any case, after this early miracle of cauterization (an idea already known for at least 200 years) Hubertus became known as the "go to man" for those seeking protection against rabies and infection from animal bites.
After Hubertus' death and canonization, people began making pilgrimages to Saint Hubert's old abbey where the monks sold the faithful small iron spikes known as "the keys of Saint Hubert". These ‘keys’ were often hung in houses and hunting lodges as a ward against rabies and as a quick-to-find "cure" for an animal bite. As in the original story, these iron spikes were to be fired until red hot and then placed directly into the bite wound to cauterize it.
Today, Saint Hubert is considered both the patron saint of hunters and the patron saint of rabies prevention.
As for cauterization, it remains a way to sterilize and staunch the flow of blood in emergencies and in certain kinds of medical procedures.