A souterrain, to use the proper term, is an artificial underground structure, typically built during the early medieval period in Ireland, consisting of one or more chambers connected by low crawlways and constructed from dry-stone walling with large capstones laid across the top. Their precise purpose has long been debated. Cold storage, refuge during raids, concealment of people or valuables, perhaps some combination of all three. The one at Clashganniv is recorded as a confirmed monument, quietly occupying its place in the Kerry landscape.

Souterrains of this kind are closely associated with ringfort settlements, the enclosed farmsteads that were the dominant form of rural habitation in Ireland from roughly the sixth to the twelfth centuries. Kerry has an unusually dense concentration of both ringforts and their associated underground structures, a reflection of the county's historically strong Gaelic farming communities and the particular geography of its interior. The townland name Clashganniv, like many Irish placenames, likely preserves an older Gaelic description of the local landscape, though the precise detail of what was here, who built it, and when, remains unrecorded in any publicly available form at present.