Passage tombs are megalithic structures, large stone constructions built without mortar, in which a narrow stone-lined corridor leads to a burial chamber. They date broadly to the Neolithic period, roughly 4000 to 3000 BC, and the builders who raised them pre-date writing, metal tools, and the wheel on this island.

The principal scholarly record for this site comes from Seán Ó Nualláin's Survey of the Megalithic Tombs of Ireland, Volume V, published by the Stationery Office in Dublin in 1989 and dedicated entirely to County Sligo. Sligo is exceptional in this regard: it holds a remarkable concentration of megalithic monuments, most famously the great cemetery on the Carrowmore plateau and the hilltop cairn of Knocknarea. Ó Nualláin's county-wide survey placed individual sites like the Barnasrahy tomb within this broader regional pattern, cataloguing the structural details, orientation, and condition of monuments that might otherwise remain known only to local farmers and passing walkers. The effort to document these sites systematically was itself a recognition that many were at risk of being overlooked entirely, their stones cleared for field boundaries or simply sinking quietly into the bog.