Lissaphuca, in the townland of Letterbrock in County Mayo, carries within it two Irish words that point toward something old and, in the older imagination, something unsettling. "Lios" refers to a ringfort, one of the thousands of roughly circular enclosures built across Ireland from the early medieval period onward, typically as enclosed farmsteads surrounded by an earthen bank and ditch. "Púca" is rather more difficult to categorise: a shapeshifting spirit of Irish folklore, capricious and not entirely trustworthy, associated in popular tradition with liminal places and after-dark wandering. A ringfort named for a púca was not, in the minds of those who named it, a place to treat casually.

Ringforts bearing the púca association appear scattered across the Irish landscape, and they tend to share a particular quality in local memory: they were left alone. Farmers who might otherwise level an inconvenient earthwork for tillage often exempted the fairy forts, as they were commonly known, from clearance. This blend of practicality and unease meant that many such sites survived the dramatic agricultural transformations of the eighteenth and nineteenth centuries intact, or close to it. Letterbrock sits in the west of Mayo, a landscape shaped by blanket bog, the Partry Mountains to the south, and the long reach of Lough Mask nearby, a region where Gaelic placename traditions persisted with particular tenacity and where the older layers of the landscape were never entirely smoothed over.