The origin of the city of Finias (or Findias) has nothing to do with Wicca, and everything to do with The Book of Invasions, a medieval manuscript written in Middle Irish. According to this pseudo-historical book, the Tuatha de Dannans came from four cities from the north: Finias, Murias, Gorias, and Falias. From those four cities, the Four Treasures of the Tuatha de Dannans were forged:

Sometimes Finias and Gorias are switched, depending on who's giving the information.

There has been some speculation that as the goddess Danu, who gave her name to the de Dannans, is identified with the Danube, then perhaps there were once four cities of the Celts on the banks of that river, where these people lived before moving west towards Ireland.