Today is celebrated as St Knut's Day in Sweden and Finland – you can find out more about it here.
When I was reading about it earlier today, it struck me that the bits of the celebrations involving the Finnish character Nuuttipukki are very similar to the Mari Lwyd folk custom found in South Wales. When I worked in Cardiff in the second half of the 90s, this was still performed in Llangynwyd, and maybe a few more villages in the Maesteg area, but I don't know whether that's still the case.
Does that suggest that both have their roots in a pre-Christian ritual, perhaps connected to the middle of winter? I'm not sure, really, but at first glance that seems the most likely explanation.