The popular name Sheehan or Sheahan, often referred to in the USA as Sheen or Shean, is the anglicisation of the Irish Ó Siodhacháin, from a diminutive of siodhach, meaning ‘peaceful’.
The eponymous ancestor of the family is disputed, but must have been unique among the Irish of the day to have deserved the description “peace maker”. Not every scholar accepts this origin of the name, but given the fact that the sept’s traditional coat of arms features a dove of peace, there will be few of the name who will want to consider any alternative. One ancient genealogy places the sept’s ancestor as a brother of Brian Boru while another has him as a member of the Scanlan sept. The Book of Leinster refers to “Muintir Sidechain” from a distant relative of Brian Boru.
Cormac Cas was King of Thomond (Tuathmhumhan, modern county Clare with adjacent parts…
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