Dedu mac Sin

Deda mac Sin (Deda, son of Sen) was a prehistoric king of the Érainn of Ireland, possibly of the 1st century BC. Variant forms or spellings include Dedu, Dedad, and Dega. He is the eponymous ancestor of the Clanna Dedad, and may also have been a King of Munster.

Through his sons Íar mac Dedad and Dáire mac Dedad, Dedu is an ancestor of many famous figures from legendary Ireland, including his "grandsons" (giving or taking a generation) Cú Roí mac Dáire and Eterscél, "great-grandsons" (again) Conaire Mór and Lugaid mac Con Roí, and more distant descendant Conaire Cóem. A third son was Conganchnes mac Dedad. Through these Dedu is also an ancestor of several historical peoples of both Ireland and Scotland, including the Dál Riata, Dal Fiatach, Múscraige, Corcu Duibne, and Corcu Baiscind, all said to belong to the Érainn (Iverni), of whom the Clanna Dedad appear to have been a principal royal sept.

The generations preceding Dedu mac Sin in the extant pedigrees appear artificial. Eventually they lead through Ailill Érann to a descent from Óengus Tuirmech Temrach and thus a distant kinship with the Connachta and Uí Néill, whose own pedigree is in fact unreliable before Túathal Techtmar.

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