"Chirurgeon" means, according to Samuel Johnson's dictionary, "One that cures ailments, not by internal medicines, but outwards applications. It is now generally pronounced, and by many written, 'surgeon.'"
The word comes from "hand" and "work." So, a surgeon uses his hands to work on a patient. In medieval times, surgeons were often barbers and butchers and learned their "trade" by hands-on experience. After the Restoration, though, according to "The Chirurgeon's Apprentice," their advocacy of "practical" medicine---cutting out the infections instead of treating them with medicines of questionable efficacy, elevated them within the medical community to be more equal with physicians (who got their name from their use of "physics," or emetics).
At The Chirurgeon's Apprentice, you can read more about "the horrors of pre-anaesthetic surgery." However, Madame L warns her Dear Readers, most of the stories told there are gruesome and should not be read on a full or squeamish stomach.