The depression may be what surveyors call a partially collapsed souterrain, one of the underground stone-built passages or chambers that were constructed throughout early medieval Ireland, typically as places of refuge, cool storage, or escape. The uncertainty is part of what makes the site interesting: without excavation, the ground keeps its own counsel.

The ringfort to which this feature belongs, recorded under the reference MA100-051, is the kind of enclosure that dots the Irish landscape in the hundreds, the remnant of a defended farmstead from roughly the early medieval period. Souterrains were often built in association with exactly these sorts of settlements, sometimes running beneath the interior, sometimes extending outward under the enclosing bank. At Drumnashinnagh, the stone-lined character of the depression is the principal clue that something deliberately constructed lies beneath or just below the surface, rather than a simple natural subsidence. D. Lavelle's archaeological survey of the Ballinrobe district, published in 1994, flagged the feature, though cautiously, noting only that it may be a souterrain rather than confirming it as one.