In Irish, "caiseal" refers to a stone cashel or enclosure, a circular dry-stone wall typically built to define a settlement or protect livestock, while "dubh" means black or dark. That the place retained this name suggests the structure here was prominent enough, and old enough, to become the landscape itself in the minds of those who lived beside it.

Enclosures of this kind are scattered across the west of Ireland, many of them dating from the early medieval period, though some have origins reaching further back into prehistory. In County Mayo particularly, where bogland has both preserved and obscured ancient features, such sites can survive as subtle rises or collapsed stone lines in the ground, their original form legible only to a careful eye or an aerial photograph. The Cashelduff enclosure sits within this broader pattern of settlement archaeology, a reminder that the land was organised, bounded, and inhabited long before any written record took note of it.