Megalithic tombs are among the oldest surviving human constructions in Ireland, built during the Neolithic period as places of burial and, most likely, ritual. They come in several forms, among them portal tombs, court tombs, and passage tombs, each with its own architectural logic and regional distribution. Mayo has a notable concentration of such monuments, particularly court tombs, which consist of an open forecourt leading into a roofed stone gallery, the whole originally covered by a long cairn of stones or earth.

Béal Deirg Mór as a place-name carries its own quiet interest. In Irish, "béal" generally refers to a mouth or an entrance, often applied to river mouths or passes, while "deirg" derives from "dearg", meaning red. The name alone suggests a landscape with a distinct character, likely shaped by the boggy, iron-rich terrain common to this part of Connacht. Beyond the tomb's existence and location, detailed records for this particular monument have not yet been made publicly available, which places it in a category familiar to anyone who has tried to trace Mayo's older archaeology: present in the official record, but not yet fully described within it.