The house itself dates to around 1800, but the plaque is more than a century and a half older, dated 1644, and carries enough heraldic and devotional detail to suggest it once marked something considerably more significant than a yard entrance.

At its centre is a heraldic shield bearing the coat of arms of the Butlers of Dunboyne, one of the many branches of the powerful Butler dynasty that dominated much of Munster through the medieval and early modern periods. A crescent sits at the centre of the quartered shield, a heraldic convention indicating a second son, or a descendant through a second son's line. The initials TB and KB appear on the plaque, though despite the specificity of that crescent device, Burke's Peerage yields no obvious match among the Dunboyne Butlers. Along the base runs a Latin inscription, IGNEM SUI AMORIS ACCENDAT DEUS IN CORDIBUS NOSTRIS AMEN, which translates as "Let God kindle the fire of his love in our hearts, Amen," a prayer associated with the feast of Pentecost. Above the shield, an ogee, the S-curved arch form common in late Gothic decorative carving, frames the monogram IHS, a Christogram derived from the Greek name for Jesus and widely used in Catholic devotional contexts of the period. The ogee terminates at each side in a rolled scroll.

The most plausible original home for the plaque is Carigateiry Castle, a now-lost fortification that appears on the Down Survey map of 1655 to 1658, the ambitious land survey commissioned under Cromwellian administration to document Irish landholdings. On that map, the castle is shown in the vicinity of what is now the Greenmount townland, or just to the south in Garrancasey townland, placing it close enough to Kenilworth House to make the connection reasonable. Whether the plaque was removed before or after the castle fell out of use, and by whom, remains unanswered.