While doing some family tree work, I came across a guy in English history, that was an M.D. or roughly the equivalent (not really sure of how that all worked in that era), with the same last name. Whether he is my ancestor or not I dunno, but it got me curious.
In this work, Physicians and Irregular Medical Practitioners in London 1550-1640 Database., he is listed as a person who essentially investigated doctors who had complaints registered against them, or were reported to be working without "joining the college". This indicates that there was a system of regulation and essentially a licensing board in existance for the practice of medicine established enough to maintain records and standards as at least as early as the mid-16th Century in England.
How far back does the idea of professional licensing and regulatory bodies go back?
One place to start looking would be the origin of medieval craft guilds. The guild designation of Master Craftsman is a type of credentialing, and they often tried to prevent non-members from practicing the craft at all. Although, the guilds were more all-encompassing than modern standard bodies, since they also acted as trade schools, unions, fraternities, and lobbyists.
I wouldn't be surprised if the "college" your (potential) relative refers to is actually closer to a guild than a modern accreditation board.