What it covers, however, is a spring with a documented history stretching back at least to the early nineteenth century, and likely much further. The well house is built from mortared limestone, and water still moves through it, emerging from an arched opening into a narrow stone-lined channel before draining away. The keystone above that arch is dated 1816, making the covering itself a piece of early nineteenth-century civic or devotional infrastructure, depending on how one reads its purpose.

The well appears by name on the Ordnance Survey six-inch map of 1837, labelled simply as Sunday Well, which suggests it was already well known and clearly identified in the landscape at the time of the first systematic mapping of Ireland. By the time the more detailed twenty-five-inch Ordnance Survey edition was produced in 1910, the entry had been updated to read Sunday Well (Covered), confirming that the limestone well house visible today was already in place and recognised as a feature worth distinguishing from an open spring. A 1983 description records the spring as confined to an area of approximately two metres by one metre at that point, a modest footprint for something that gave a whole road its name. Wells named after days of the week, particularly Sunday, were often associated in Irish tradition with patterns, which were gatherings held on a saint's feast day or on a fixed day of the week for prayer, socialising, and the drawing of water believed to have curative or blessed properties. Whether that tradition directly shaped the naming here is not recorded, but the combination of a covered spring, a named road, and a datestone suggests the well mattered enough to be formally maintained.