Before they converted to Christianity and adopted the Roman calendar, the early English (‘Anglo-Saxons’) reckoned time using a system of lunar months. Each cycle of the moon, probably from full moon to full moon, was a month. The year began at the winter solstice, the shortest day of the year. There were two seasons, summer, when the days were longer than the nights, and winter, when the nights were longer than the days (See my earlier post for a summary of the early English calendar.)
The fifth month of the year, corresponding approximately to the Roman and modern month of May, was called Thrimilchi. Bede, writing in 725, tells us:
Thrimilchi was so called because in that month the cattle were milked three times a day; such, at one time, was the fertility of Britain or Germany.--Bede, On the Reckoning of Time, Chapter 15. Translated by Faith Wallis.
This might be literally true. As far as I know, lactation is a continuous process so presumably a cow could be milked three times a day instead of the usual two if that happened to be convenient. It might also be a variant on the “Lost Golden Age of Far Away and Long Ago” which humans have a tendency to look back on with longing, regardless of whether it really existed. Nostalgia never goes out of fashion.
However, the month name might reflect the sudden availability of fresh pasture and fresh dairy products after the long months of winter. In lowland areas of Britain the grass usually starts to grow by April – which end of the month depends on latitude, local climate and weather – and is getting quite lush by May.
In areas with upland grazing, May corresponds to the time of year when livestock can be moved up to hill pastures. In the Lake District, Pennine hills and North York Moors the snow has gone even from the summits by May in most years and the vegetation is starting to grow strongly enough to withstand the attention of hungry sheep and cattle. Even in the Scottish Highlands, further north and higher altitude, the snow has melted and the grass started to grow again by May in all but the highest corries. This frees up the low valley fields to be cropped for hay (or, these days, silage). It has been suggested that cows grazing outdoors on fresh grass produce milk with higher nutritional content than cows fed on silage and concentrate, and anyone who's ever been into a French cheese shop will have noticed that cheese such as Beaufort produced "a l'Alpage" (from cows grazing on upland pastures) carries a noticeable price premium over the same cheese produced during the winter when the cows are living indoors (I daresay this is partly just marketing, but it does taste nicer too).
After the long dark months of winter, when people had been living on probably limited and almost certainly rather dull supplies of dried or salted produce, the sudden appearance of milk, butter, cream and cheese must have been a most welcome addition to the diet. Not so surprising if it was commemorated in the name of the month!
Bede: The Reckoning of Time. Translated by Faith Wallis. Liverpool University Press, 1999, ISBN 0-85323-693-3.