Thanksgiving, Turkey Day, Food and Sleep Day… Most Americans will spend most of today in some variant of a ritual that’s not quite 400 years old and still evolving: the turkey and the idea of the feast of thanks are probably the only constants.
That the day echoes English harvest festivals from the 16th century is no coincidence, any more than the way those festivals have their roots in pre-Christian harvest festivals (and transferred more than a few practices pretty much intact although the origins of them is long-gone). And yes, it is a whole lot more complicated than that, but it makes a decent enough starting point.
The thing is, practically any society-wide tradition you can name is is likely to be either a direct descendant of something much older or a spiritual descendant of sorts with its roots in one or more much older traditions. Celebrating and giving thanks for a successful harvest by means of either a feast or sacrificing massive quantities of food to a deity (in the case of the US thanksgiving, you could argue it’s both and the sacrifice is going through our stomachs).
The same thing is going to apply when writing: any fictional festival will have roots in one or more older fictional festival, including practices that nobody now really understands but still have to happen because it’s “traditional” (The corn dolly in many English thanksgiving festivals comes to mind – it’s a relic of using the last sheaf to make a talisman that would be ritually sacrificed the following year (and the harvest in question wasn’t corn as we in the US understand it: the English use “corn” to mean any kind of grain) and was – at least for some cultures – thought to be the winter home of the grain spirit).
We do this ourselves – the tale of the woman who always cut the end off the leg of lamb to roast separately because her mother did it and her mother did it, never realizing that the grandmother cut the end off because her baking pan wasn’t large enough to take the whole leg resonates precisely because we all do exactly this kind of thing. How many of the women here arrange their kitchens more or less the way their mothers do? Until I wound up with a kitchen that didn’t have the right configuration for it, I certainly did (tea towels in the third drawer. Never shalt they reside in the second drawer for that is for cooking utensils).
How many of us even stop to think that we do something because that’s the way our parents did the same thing? Of such are traditions made, and traditions followed until the meaning is lost become rituals.
Thanksgiving in the US is certainly well on its way to that: with the year-round availability of practically everything, seasonal foods have lost their meaning to the point that many people couldn’t tell you that the traditional thanksgiving dishes are all seasonal and mostly late-harvest items – particularly in the northeast where the tradition got its more or less official start.
And yes, you can thank northeastern USA (specifically Philadelphia) for that other US thanksgiving tradition as well – Black Friday…