The Irish name gives a clue: Bohergarránban, roughly "the road of the white horse ridge", an ancient causeway that once carried travellers in a straight line across the marshes between the old church of Dysert and the settlement at Rattoo. By the time the later Ordnance Survey editions were produced, the road had been quietly dropped from the maps, yet it never disappeared. It is still visible on the ground, running in measured straight sections, each consistently 2.75 metres wide, for a total traceable length of 1,830 metres.

When the Ordnance Survey's John O'Donovan passed through in 1841, he recorded the road by its local English name, White Horse Ridge, and noted that it ran through the bog from the old church of Dysert all the way to Rattoo. The broader route may have connected two significant early medieval sites: the monastic settlement at Dysert and the round tower at Rattoo. A round tower is the tall, tapering stone structure associated with early Irish monasteries, used variously as a bell tower, a landmark, and a place of refuge. Writing in 1845, the antiquarian George Petrie recorded a causeway extending from Rattoo Round Tower towards the River Brick, and the bohergarránban can be traced from the eastern side of that river onward across the marshes, suggesting the two formed part of a continuous crossing. O'Donovan also noted, with the matter-of-fact precision of a field surveyor, that in 1841 a fisherman kept a flat-bottomed boat at the river crossing to ferry passengers who wanted a short cut to Listowel via the Casán Ciarraighe, the river name he pointedly observed was being incorrectly anglicised as the Cashen.

The road's outline remains legible in aerial imagery taken as recently as 2011 to 2013, its straight geometry cutting across ground that has otherwise been shaped by centuries of drainage and agricultural change. That a causeway of consistent construction and considerable length should survive, largely forgotten except by those who walk directly over it, says something quiet and specific about how much of the Irish landscape still lies just beneath the surface of what is commonly known.