It measures roughly two and a half metres along its northeast to southwest axis and one and a half metres across, making it a modest but deliberately constructed feature, not simply a natural seep in the ground. The stonework revetment, dry-laid without mortar, is the kind of careful rural craft that tends to survive quietly for centuries without attracting much notice.

Holy wells are among the oldest continuously venerated sites in Ireland, often pre-Christian in origin and later absorbed into local Catholic practice, becoming associated with a patron saint and observed on a particular feast day through a ritual circuit known as a pattern. The wells themselves were understood to carry curative or protective properties, particularly for ailments of the eyes, skin, or general health, and the act of visiting, praying, and sometimes leaving a votive offering at the well was a deeply local affair, bound to the community of a particular townland rather than to any wider institution. The well at Tonagarraun fits this quiet, parish-level tradition, its careful construction suggesting it was maintained and regarded rather than simply stumbled upon.