Beers at Christmas have been a thing since, well before we even had Christmas in the western world. Throughout history alcohol nearly always formed a part of any celebration for reasons that should be quite obvious. But there is more to seasonal ales that some lairy druids wanting to party (although they very much did).
Winter had always been a time of ritual and celebration, with events like the winter solstice it is almost natural that people would make this a time of special events. Beers in this early period would have been quite different from what we drink now. Hops were not widely adopted and grains not properly specialised or readied. Spices, honey and maybe even bits of tree like our Logger’s Lager would have been much more common for flavouring, bittering and preserving. Pre-medieval period though we have no way to know exactly what they did drink, even in the Medieval period it can be difficult to find good records, so before that when very little was written down and many things were simply oral tradition we can only learn a general outline. As time went on though this tradition of winter beers was not lost, like many things Christianity co-opted to help bring in the west beer stayed a central feature of celebrations in the winter. Monasteries were known to be a centre of brewing and with this came specialist Christmas ales.
Partly because the lack of hops meant these beers did not last very long and partly because it was not always easy to get certain ingredients being seasonal was much more important to these beers. This is something we still see done but it is more out of tradition rather than necessity. This goes a long way to explain why the beers became so special at these times, it simply was not possible to have them at any other time of the year so they become intrinsically linked with the season and events. Food and beer was even given as gifts sometimes including to the poor, though monasteries also took advantage of this such as tenants of the town of Lagrasse. To be able to keep certain livestock including rabbits the monks ordered each family give up their best bunny as payment.
With this traditions for each region came to and this can be seen in the ales and other alcohol they drink. One thing you’ll find these beers have in common is they are very strong and very warming which is exactly what people wanted at this time. Germany has a wide range of beers for Starkbierzeit, strong beer season. Weihnachtsbier are German Christmas beers and come in all types like Weihnachtsbockbier , Festbier and also Starkbier to name a few. Many of these are sold at Christmas markets for tired and cold shoppers. Gløgg is a spiced Scandinavian wine sometimes mixed with spirits, it features cardamom, cinnamon sticks and even some orange peel. Denmark has Juleybryg, Nisseøl and Påskeøl. A brand of Julebryg called Tuborg is only available for 10 weeks it is the 4th best selling beer in the country, releasing with the annual J-day since 1990 making it a more modern tradition.
So new and old ale has always be a central part of winter and the celebrations that come with it.