Or at least you’re not as right as you think you are. I, too, used to believe that “brewster” meant, exclusively, a female brewer, until a discussion recently on the excellent wordorigins site about the word spinster. Someone put up the Oxford English Dictionary entry on the –ster suffix which revealed that it wasn’t as simple as I had thought:
In northern M(iddle) E(nglish), perh. owing to the frequent adoption by men of trades like weaving, baking, tailoring, etc., the suffix [-ster] came very early to be used, indiscriminately with -ER, as an agential ending irrespective of gender…
It is probable that “-ster” was often preferred to “-er” as more unambiguously referring to the holder of a professional function, as distinguished from the doer of an occasional act. In Scotland, baxter and webster survived as masculines down to the 19th c. …
In the south the suffix continued to be predominantly feminine throughout the M(iddle) E(nglish) period. The Old English formations, baxter, seamster, tapster, were in southern English usually feminine before 1500 … also spinster, which alone of the group has survived (though with change of sense) solely as a feminine…
In other words, if you see “brewster” in a Southern English context in the Middle Ages, it probably means a female brewer, but in the North of England and Scotland it could be female, it might just as likely be a male.
The geographical spread of “Brewster” and “Brewer” as surnames seems to confirm this North-South divide for brewster/brewer. Another excellent site, National Trust Names, which tracks the frequency of surnames in different parts of the country, reveals that Brewster, even in the late 19th century, was very much an East of England name, from Essex up to the East Riding, with a small concentration in Aberdeen/Highlands/Fife. Brewer, in contrast, was very much West Country and South Central England, with a small concentration in South West Essex but no real presence north of about Oxford, except for small areas of Lancashire and Lincolnshire,
In apparent confirmation that this is telling us something meaningful about “–ster” versus “–er”, Baker as a surname in 1881 is, similarly to Brewer, solidly concentrated in the south of England, while the surname Baxter is, yes, huge in Scotland, and down the eastern side of England as far as Suffolk.
Webber and Webster (both meaning weaver) are just the same – Webber strongest in the West Country, Webster in Scotland and the North of England, but no presence in the South. So in surname-forming times (mainly the 13th and 14th centuries) it does look as if the “-er” form of the agent suffix was preferred in the south, particularly the south west, and the “-ster” form in the north, the east and Scotland
What this means for brewing historians is that we can’t take references to “brewsters”, particularly northern and Scottish references, as being solely concerning female operatives. Sometimes this can be important: if you’re looking at, say, borough by-laws that only mention restrictions on “brewsters” you might think there weren’t any male ale-makers about, when in fact “brewsters” was meant to cover both sexes.
This also explains better the expression “brewster sessions”, the name given to the (former) annual meeting of licensing magistrates in every district that renewed pubs’ licenses to sell alcohol by retail. It always puzzled me why the “feminine” word was used – but if “brewster” covers both sexes, then that makes more sense.
Incidentally, another great website, yournotme.com says today there are about 9,500 people with the surname Brewer in the UK, and 4,500 Brewsters. And 3,251 Drinkwaters … (hello Ian …)