Just an addition to bozon's w/u:

According to the Annals of the Four Masters, the Tuatha de Dannan invaded Ireland in the Anno Mundi 3303, which is roughly 701 BC1. They came from four cities:

Each of the Tuatha had to have a position in that society. Some of the most important were:

The Tuatha de Dannan could only be ruled by he who is physically perfect (an idea we see later in the Fisher King). Their successive rulers over Ireland (according to the Annals of the Four Masters) are said to have been:

At this point, the Tuatha were driven underground by the Milesians, at which point Bodb Dearg, son of the Dagda, became king; this drove Lir to nearly leave the island. However, Lir is not Tuatha anyway. No, Lir and his family are a seperate group from the Tuatha de Dannan. This may be because Lir, Manannan, et al., are oceanic gods, and the Celts were originally land-locked. They were already on the island before the Tuatha came. It's also been questioned whether the Morrighan is specifically Tuatha also.

When one reads The Book of Invasions, one sees a history of successive invasions of Ireland by different tribes. It is entirely reasonable that this history is in fact based on fact--and evidence will support that Ireland did see several invading populations before the Christian era.

This said, the Tuatha de Dannan are literally the Tribe of Danu, tuath meaning tribe (see Deutsch). Now, Danu is the mother goddess of the Celts, but she never appears in the Irish histories. However, she did give her name to the Danube in Germany. Now:

  • the reason Danu does not appear in the Irish sagas is because she is not in Ireland
  • it is known the Celts had lived along the Danube (and possibly even gave Vienna its name)
  • the Tuatha de Dannan are said to have come from four magical cities: Murias, Finias, Falias, and Gorias

It is entirely possible that the mythical Tribe of Danu are in fact the Tribe from the Danube, and are one of the first Celtic2 invaders of Ireland; the designation of them as gods is a form of ancestor worship, which can also be seen in their supposed living in sidhe--hollow hills or burial mounds.

  1. The designation of 701 BC also corresponds to what archaeologists believe is the rough age when the Celts first came to Ireland, thus making my point about the Tuatha de Dannan being the first Celtic wave.
  2. There has never been a satisfactory definintion of what a Celt is racially; I use the term culturally, and even then loosely.