A souterrain is an artificial underground passage or chamber, typically constructed during the early medieval period, between roughly the sixth and twelfth centuries. They were built from stone, often lined and roofed with large slabs, and are found in association with ringforts and other settlement sites. Their precise function is still debated: cool storage for dairy produce, refuges during raids, or simply ancillary spaces attached to a farmstead. Whatever their original purpose, they represent a considerable investment of labour, and their presence in a townland is usually a sign that someone of some standing once lived nearby.

Callanafersy sits in a part of Kerry that was densely settled during the early medieval period, a landscape still scattered with the earthwork remains of ringforts and the occasional ogham stone. The particular souterrain recorded here has not yet had its full details made available, which means the finer points of its construction, dimensions, and condition remain unconfirmed in the public record. What is certain is that it has been identified and recorded as a monument, placing it within a long tradition of underground structures found throughout Munster and beyond.