The Tuatha Dé Danann are the early gods of Ireland, associated with the great sídhe or passage-mounds of Brú na Bóinne. There is some debate about their original name, whether it was Tuatha Dé Danann or just Tuatha Dé, and attempts have been made to link them with the Tribe of Dan, one of the 12 tribes of Israel. Anthony Murphy briefly investigates.
I've seen it stated on more than one occasion over the years that the Tuatha Dé Danann were originally just known as the Tuatha Dé, and that the Danann bit was added later, in the 18th or 19th centuries. This is not true. In the Lebor Gabála (commonly known as the Book of Invasions), they were Tuatha De Danand in the Irish, abbreviated to Tuatha d.d. The Lebor Gabála was written down in the Book of Leinster (Lebor na Nuachongbala) in the 12th century. The photo shows a passage from the Lebor na Nuachongbala, (TCD MS 1339, p.9), which reads in the Irish:
Combtar iat Tuatha d.d. tancatar Herind.
So that they were the Tuatha De Danand who came to Ireland.
However, it is true that the divinities were often referred to in the shortened form of Tuatha Dé. Dáithí Ó hÓgáin (The Lore of Ireland, 2006, p. 478) says this designation is very old and that although its import in Irish is something like "divine communities", its original meaning was probably more specific.
MacKillop (Oxford Dictionary of Celtic Mythology) says the origin of Danann is still disputed. He adds that the phrase Tuatha Dé predates the Lebor Gabála, and described both the Israelites in translations of the Bible and the old gods. Undoubtedly this association of the phrase Tuatha Dé with the Israelites has helped fuel a widespread theory (propagated mainly on the internet and not in scholarly works) that the Tuatha Dé Danann are, in fact, the Tribe of Dan, one of the twelve tribes of Israel. However, the phrase Tuatha Dé literally means people, tribe or nation (tuatha) of god, or more likely "gods" (dé).
Given that the scribes of the medieval manuscripts were largely Christian monks, it seems odd that if the Tuatha Dé Danann were the Tribe of Dan that this fact would be completely concealed, especially given the propensity of the scribes to link ancient Irish history with Biblical figures. For instance, in the case of Cessair, the first to arrive in Ireland according to the Lebor Gabála, she was said to have been a granddaughter of Noah (he who built the ark at the time of the great flood).
Tribe of Dan
In any case, the proposed "evidence" that the Tuatha Dé Danann were the Tribe of Dan is extremely circumstantial, and in most cases completely untenable. A great number of websites make very spurious claims that Irish place names were left by the Tribe of Dan, as a sort of secret record or trail of their journey (described as a serpentine trail because of Dan's connection with the serpent in the Old Testament). To give an example, the oft-quoted Herbert W. Armstrong said "the Tribe of Dan's waymarks can be found in place names such as Dundalk, Dundrum, Donegal Bay, Donegal Cit, Dunglow, Londonderry (Derry) and Dingle".
However, in many of these cases the root word is Dún, meaning a "fort". The idea that Irish place names beginning with Dun and Don are, in fact, secretly related to a mysterious race called the Tribe of Dan is completely without factual foundation. However, the internet "scholars" write very serious blog posts, quoting disreputable sources, and the unfortunate results get propagated as fact widely across the internet.
I plan to write a more comprehensive blog post about this subject in the future.
View the Lebor Gabála manuscript pages on the Irish Script on Screen website.