That road survives as an earthwork today. The lake, Lough Iron, once came to within 280 metres of the priory; the Inny River drainage scheme of the late 1960s pushed the shoreline back to 650 metres, and a conifer plantation now occupies the ground in between, quietly erasing what would once have been an immediate and defining relationship between the community and the water.

The Augustinian priory of Tristernagh, sometimes called the Priory of Kilbixy and dedicated to the Blessed Virgin Mary, was founded in the late twelfth century by Geoffrey de Constantine of Cosmeston Castle in Glamorganshire. Geoffrey had received lands in the territory of Kilbixy from Hugh de Lacy, the Anglo-Norman magnate who held the Lordship of Meath and distributed portions of it to followers as part of the process of Norman settlement known as subinfeudation. The charter granted to the priory was substantial: four carucates of land adjoining the site, islands in Lough Iron, a water mill, fisheries, a toft in Balyrothy, a messuage near Dublin, seven named churches across Meath and Dublin, and the right to elect their own prior. Simon Rochfort, Bishop of Meath, further granted the priory the privileges of a free churchyard. By the taxation of 1302 to 1306, the priory's possessions were valued at £15 11s. 4d. By 1411, Pope John XXIII was issuing indulgences to those who visited and gave alms for its repair, suggesting the buildings were already under strain. The monastery was surrendered on 30 November 1539 by Edmund Nugent, who held the peculiar combination of offices of prior, commendator, and Bishop of Kilmore, and its lands were almost immediately dispersed. A 21-year lease went first to Robert Delman of Dublin, then in 1562 to Captain William Piers, seneschal of Clandeboy, who was required under his lease terms to maintain two able English horsemen on the property and to sub-let only to those of English parentage or born within the English Pale. By 1609, King James I was granting the site to Adam Loftus of Rathfarnham Castle, by which point the priory's medieval world had been comprehensively dismantled and parcelled out across successive decades of Tudor land management.