It never appeared on the Ordnance Survey six-inch maps as a recorded antiquity, which is unusual enough, but the more striking detail is that when surveyors arrived in 1985 they were turned away at the gate. The landowner refused them access, and so the site passed into the record books as something glimpsed from the outside, noted down, and left unresolved.

The Castleisland District Archaeological Survey of 1985 described it as a fort, the term most commonly used in Irish fieldwork for a ringfort, a type of enclosed farmstead typically dating from the early medieval period, built of earthen banks or stone to define a homestead and offer some protection for livestock. Whether the Knocknadarriv example fits that description in any detail remains unclear, because the aerial photography taken between 2011 and 2013 shows no visible outline of a structure at all. Whatever may once have been there has either been levelled, altered beyond recognition, or was always more ambiguous on the ground than the label suggested. Local tradition, collected from Lackbrooder School as part of the Irish Folklore Commission's Schools' Collection, knew the place by a different name entirely: a Fairy Fort. That designation, common across rural Ireland for ringforts and enclosures believed to be inhabited by supernatural forces, often functioned as a form of protection in itself. Sites called fairy forts were frequently left undisturbed, not out of official preservation instinct but out of a deeper, older reluctance to interfere with what might be watching back.