Lios an Iarla translates as "ringfort of the earl", and the tradition attached to the site is specific enough to linger: according to local memory, the Earl of Desmond sheltered here during the desperate final years of the Desmond Wars, using the ancient enclosure as cover while trying to evade the forces closing in on him.

A rath, or ringfort, is a type of enclosed farmstead built in earthen construction, common across Ireland from the early medieval period. Most were domestic in origin, used by farming families who valued the security of a raised bank and surrounding ditch. The example at Lissanearla is univallate, meaning it has a single enclosing bank rather than the multiple rings sometimes found at higher-status sites. That bank is substantial: roughly eight metres wide at the base and rising up to three metres above the interior floor level. A U-shaped fosse, the external ditch that runs around the whole site, adds further definition to the circuit. The interior measures approximately forty metres across, and its floor sits noticeably higher than the surrounding ground, giving the site a slightly elevated quality that would have made it useful for anyone wishing to observe the surrounding countryside. Near the centre, the foundations of a sub-rectangular house are still visible on the surface. The entrance, about seven metres wide, appears to face south-east. If the Desmond association is accurate, the fugitive earl, Gerald FitzGerald, the fourteenth and last Earl of Desmond, would have been using a structure already many centuries old when he concealed himself within its banks. He was eventually killed in 1583, and the Desmond lands were subsequently forfeited to the Crown, reshaping landholding across Munster for generations. Whether the fort offered him any real protection, or simply a brief pause in his flight, the place has held onto his name ever since.