The folkloric tradition behind the name tells of the lovers Diarmuid and Gráinne, who, according to legend, fled across the country after Gráinne eloped with Diarmuid on the night of her betrothal to the warrior Fionn Mac Cumhaill. Any ancient stone structure large enough to shelter two people could attract the name, and this one in Tyredagh, tucked onto a west-facing shelf above a small stream and beneath low limestone cliffs, is no exception. What makes it quietly anomalous is that it resists easy classification: its gallery runs roughly north to south rather than following the east-west alignment more typical of the region's megalithic tombs, and scholars have debated whether it might be better understood as a court cairn, a form of Neolithic communal tomb usually defined by a forecourt area that opened onto a roofed gallery.

The structure itself is a gallery tomb, meaning the burial chamber takes the form of an elongated roofed passage defined by large upright stones called orthostats, with flat capstones laid across the top. At Tyredagh, the gallery measures roughly 5.6 metres north to south and 2.2 metres east to west. Two large orthostats survive in place on the eastern side, while the western side retains one large and three smaller uprights, the largest standing 1.25 metres high. A substantial flagstone, over two metres long, lies partially sod-covered at the northern end; this is thought to be a displaced capstone that slipped from its position, likely when the eastern side stones shifted. A second buried flagstone nearby may have served as a secondary capstone. The interior is sunken and uneven, suggesting the ground was disturbed at some point, possibly long ago. Ruaidhrí de Valera and Seán Ó Nualláin documented the monument in their 1961 Survey of the Megalithic Tombs of Ireland, and an earlier plan by the antiquarian Thomas Johnson Westropp informed the interpretation of it as a possible court cairn. A wedge tomb, a different form of megalithic monument dating to the later Neolithic and early Bronze Age, lies approximately 450 metres to the southeast.

The setting rewards careful attention. The monument sits on a slight natural mound in rough, poorly drained pasture, and the surrounding vegetation, including trees and encroaching scrub, partially obscures both the stones and a scatter of large boulders on the slope between the tomb and the stream below, some of which may originally have been part of the structure. Animal burrows have further disturbed the interior. The limestone cliffs that frame the valley on either side give the place a sheltered, enclosed quality that makes it feel older than it looks.