Annals of the Four Masters

The earliest written references to Lough Sewdy in the Annals of the Four Masters, as in most such cases, are brief. In 600 A.D., we read that Colman Rimidh and Aedh Slaine, 'after six years in the sovereignty of Ireland' were killed at 'Loch Semhdidhe'.

In 1034, Murchadh Ua Macleachlainn 'was treacherously slain' by Mac Iarnain, the chief of Ciurcne, 'on the island of Loch Semhdidhe'. Conchobhar Ua Briain (Conor O'Brien) led an army of Munster men into Leinster and Meath in 1131 and reached Lough Sewdy, which they plundered. Another episode of conflict occurred in 1159 when it was reported that an army led by Ruaidhri Ua Conchobhair (Rory O'Connor), a battalion of Thomond men and the army of Tighearnan Ua Ruairc of Breifne, invaded Meath and reached Lough Sewdy. This incursion was in response to the death of O'Conor's son in a battle against the king of Meath who had tried to prevent the building of a bridge at Athlone.

The first reference to 'Baile-Mór Locha-Semhdidhe' ('the great town of Lough Sewdy') may be found in 1450 when it was the scene of yet another violent incident - this time when Mageoghegan's son, in the course of plunder, killed Brian, son of Laoiseach, at Ballymore-Lough Sewdy.

The last mention in the Annals of the Four Masters is found in 1598, when O'Rourke and Red Hugh O'Donnell together moved into Meath, plundering the area from Mullingar to Ballymore-Lough Sewdy, during the 'Nine Years' War'.

These entries indicate that Ballymore-Lough Sewdy was of strategic importance in the middle ages. It has been suggested that it was the site of a bruighean or hostel, which is credible given the evidence.