Fyrnsidu is one of various names used to refer to the reconstruction of Anglo-Saxon polytheistic beliefs. It is Old English for “old custom”. Some use the plural, Fyrnsida, or Anglo-Saxon Heathenry (“ASH”) as well. More generically one could also call it simply Heathenry, which also includes the other Germanic groups, or Heathendom, which accomplishes the same, but without a foreign suffix. Those who are practitioners of Fyrnsidu may often refer to themselves as Fyrnsidere meaning “Follower of the old way/custom”.
The religion is related to Ásatrú, the reconstruction of Norse polytheistic beliefs. It’s Ásatrú that many people find first due to its increased visibility in the public, however slight that might be, which in turn leads people to find the various related Germanic religions. Other groups have other terms for themselves, such as Forn Siðr, which is the Old Norse cognate to Fyrnsidu, or Urglaawe, the religion of the Pennsylvania Dutch.
Followers in need of help may approach a variety of entities:
It is to these entities that offerings are left. A central idea is that you give so that they may give in return. This is done so that people and other beings are interconnected in a web of reciprocity, which will strengthen bonds and protect. Offerings to ancestors, wights, and gods may be left outdoors, buried, thrown into rivers, burned, and/or broken. The importance is put upon the items’ irretrievability so that it may not return to human hands.
No matter what is said or done, this is a religion that was interrupted. The gods were largely forgotten. Many practices lived on as folklore and local customs, but were no longer felt as being a part of a polytheistic religion. These may have only lived on for a few centuries, while others endured to the industrial revolution and beyond. We piece together what we can find and give worship once more. It requires a great deal of work to find evidence, but it’s a task that we often love.
(Credit to the Heargweard website for the explanation.