Who is Gambrinus?
Known as the “patron saint of beer”, King Gambrinus has long been a universal symbol of beer and brewing. A legendary European culture hero, Gambrinus is neither a saint nor a tutelary deity. Legend attributes him no special powers to bless beer nor to make crops grow; he did not invent beer nor was his reputation as super-boozer of any significance.
Among the persons theorised to be the basis for the Gambrinus character are Jean Sans Peur aka John the Fearless and Ganbrivius (1371-1419), and John I, Duke of Brabant and Flanders (c. 1252-1294).
John is Jan in Flemish and “first” is primus in Latin. So he was called Jan Primus which could have been mingled to Gambrinus. Jan was a great supporter of the brewers' guilds of Leuvin and Brussels and known for partying all night.
Count of Flanders was one of several titles of nobility held by John the Fearless. He is credited with introducing or legalising hops within the County Flanders. Prior to using hops, the Flemish, along with other Europeans, brewed with an herbal medley called gruit.
While some attribute the invention of hopped malt beer to Jean Sans Peur aka Ganbrivius other ascribe it to Jan Primus. A corruption of either name may palusibly be shown to have resulted in the present name Gambrinus.
According to legend, King Gambrinus could drink a stein full of beer in one draft. Because it was his imperviousness to drink, brewers appointed him as their patron many centuries ago.