Somewhere beneath the streets of Kilcock, northeast of the town square, there is a holy well that most people walk over without knowing it. Its rediscovery came not through archaeological excavation but through the mundane act of lifting a manhole cover, which revealed a circular shaft roughly 0.8 metres across, several metres deep, and lined with small, undressed mortared stone. The well was dry when inspected, which only adds to its quietly disconcerting quality: a sacred site folded into the modern infrastructure of a Kildare commuter town.

The well is known locally as Tubbermohocca, a name derived from the Irish for well and the saint to whom it is dedicated, St Coca, a sixth-century figure said to have been the sister of St Kevin of Glendalough. The connection to Kevin, one of the most celebrated of the early Irish saints, gives Coca a notable lineage, though she remains relatively obscure outside local tradition. The well appeared, unnamed, on the first edition of the Ordnance Survey six-inch map of 1838, which places its documented existence firmly in the pre-Famine landscape. It was apparently covered over in the mid-nineteenth century, after which it passed out of common knowledge for generations. A pattern day, the traditional Irish observance of a saint's feast with prayer, procession, and sometimes festivity at a holy well or local shrine, was held here on the sixth of June, and local tradition, recorded by Mr Michael Durkan, confirms that this custom was once kept at Tubbermohocca. The sixth of June corresponds to the feast day associated with the well's dedication.