The vegetation has grown so thickly around the site that proper investigation has been declared impossible, which gives the place an oddly stubborn quality: it appears on maps, it has a name in the archaeological record, and yet it remains effectively sealed off from scrutiny.

What is known comes from two sources separated by centuries of use. The Ordnance Survey map of 1943 marks the feature with hachures, the short radiating lines cartographers use to indicate an enclosure's raised bank or surrounding earthwork, confirming that something deliberate and circular sits on that ridge. More intriguing still is a cup-marked stone recorded within the interior. Cup marks are among the oldest forms of human mark-making found in Ireland, shallow circular depressions pecked into rock surfaces, and they are typically associated with prehistoric activity, though their precise purpose remains a matter of ongoing debate among archaeologists. The combination of a formal enclosure and a decorated stone inside it suggests the site has a long history of significance, even if the details are now inaccessible beneath the overgrowth.

The enclosure belongs to a broad category of circular earthworks found across Ireland, some of which served as ringforts during the early medieval period, others having prehistoric origins. Without being able to examine the banks, the interior, or the full context of the cup-marked stone directly, it is difficult to assign Derryduff confidently to any one period or purpose. For now, it remains a feature that the landscape has quietly reclaimed.