Nuadu Argatlám , a figure from the mythological cycle, features as king of the Tuatha Dé Danann. It is said that in the battle with the Fir Bolg at Mag Tuired (Moytirra, Co. Sligo), he lost an arm, an imperfection which obliged him to abdicate his kingship in favour of Lug. He was later given a silver arm – hence his sobriquet, ‘silver-handed’. Otherwise, he appears as the husband of Bóinn, the eponymous goddess of the River Boyne, who supposedly lived at Brug na Bóinne (Newgrange). Nuadu and Bóinn are the parents of Óengus in Mac Óc.
Nuadu is associated with the fortress of Almu (Allen, Co. Kildare), and is probably commemorated in the placename Mag Nuadat (Maynooth). Almost certainly, Nuadu was a Celtic deity, cognate with the British Nodens, while his son Óengus in Mac Óc is cognate with the British Maponos. Nodens was the focus of a cult in Gloucestershire, which apparently involved marine and solar symbolism and was associated with hunting, fishing, and healing. It has been suggested that a stone figure from Tanderagee, Co. Armagh, is an image of Nuadu; curiously, the posture of its right arm finds parallels in two images in Germany.
Apart from the fact that Nuadu is intimately connected with the kingship of Tara – his people are said to have brought the stone of Fál and the sword of Nuadu to Tara – his significance in historical terms relates only to the key role accorded to him in genealogical tradition. He is represented as the common ancestor of the Munstermen, Síl Chuinn (descendants of Conn), Ulaid, Dál Riata, Laigin (Leinstermen), and Osraige.