Blocked-up archways, sealed doorways, and filled-in windows visible in the standing masonry point to a much larger earlier structure, one that was adapted rather than replaced at some point in its history, leaving the building as a kind of architectural palimpsest. Then, in 1961, a tunnel was uncovered beneath the front lawn immediately to the south-east of the house, adding a further dimension of quiet strangeness to a site that might otherwise read simply as a handsome ruin.

The story of Kellymount appears to stretch back at least to the mid-seventeenth century. The Down Survey, a remarkable mapping project carried out between 1655 and 1656 that recorded land ownership across Ireland in the aftermath of the Cromwellian wars, shows a substantial house in the townland then recorded as 'Balleemcloughlin', which corresponds well to the modern townland of Kellymount. The family associated with the house was descended from Maurice O'Kelly of Offaly, whose line had settled in Gowran during the reign of Queen Elizabeth. The house did not survive intact through the following century; a fire destroyed it in 1750, after which it was rebuilt. That rebuilding appears to have produced a reduced version of the original, incorporating surviving walls from the earlier structure rather than starting afresh, which accounts for the blocked openings still legible in the masonry today.