A souterrain, to use the proper term, is an artificial tunnel or chamber built into the earth, typically during the early medieval period in Ireland, between roughly the sixth and twelfth centuries. They are found in their hundreds across the country, usually associated with nearby ringforts or settlement sites, and their purpose has long been debated: storage for perishables in the cool underground air, refuge in times of danger, or both.

The souterrain at Lissodeige is recorded as a monument, placing it within a wider pattern of early medieval activity that characterises much of the Kerry landscape. The county has a notable density of such underground structures, often cut into glacial subsoil or constructed from dry-laid stone slabs, their low lintelled entrances easy to miss entirely from the surface. Lissodeige as a placename carries the element "lios", the Irish word for a ringfort or enclosure, which suggests this part of Kerry was settled and organised long before any written record caught up with it. That a souterrain exists here is not surprising; that it survives at all, in a county where field clearance and drainage have erased so many such features, is quietly notable.