A drumlin is one of those smooth, elongated hills left behind by retreating glaciers, and whoever chose this particular one as the site of an enclosure had an eye for elevation and visibility. The monument measures roughly 21 metres east to west and 15 metres north to south, modest dimensions that suggest a defended homestead rather than any grand fortification, though its precise origins and age remain unrecorded.

The earliest documentary trace of the site comes from the 1835 edition of the Ordnance Survey six-inch map, where it is marked simply as a "Fort", the word Irish mapmakers and their informants routinely applied to earthwork enclosures of this kind, without implying any particular period or function. Such earthen enclosures, defined by a bank and internal scarp, are scattered widely across the Irish midlands and northwest, and many date from the early medieval period, though without excavation it is impossible to say whether this one does. What complicates the picture at Tawly is a field bank running north to south directly across the enclosure, bisecting it. At some point, agricultural reorganisation of the land cut straight through the monument, treating an ancient boundary as no obstacle at all to a newer one.