Known as Toberreendoney, a name that translates from the Irish Tobar Rí an Domhnaigh as "well of the king of Sunday", the site is today a modest thing: a concrete cover with a wooden hatch sitting over a spring. The name alone suggests some older, stranger significance, and the folklore gathered around it more than bears that out.

The fullest version of the story was recorded by schoolchildren in Tullamore between 1936 and 1937. In that account, the well originally sat in the adjoining townland of Bedford, in a field belonging to a Protestant minister, about a hundred yards from his house and close to the bank of the river Galey. When the parson's maid washed clothes in the water, the well took offence and relocated itself across the river into a field belonging to the Nolan family in Drombeg. The act of washing clothes in a holy well was widely understood in Irish folk tradition as a desecration capable of causing exactly this kind of response. The Tullamore account also names the well as Saint Agnes's well and attributes its curative reputation, specifically for ailments of the eyes, to a holy woman of that name who, while paying her devotional rounds at the well, heard a voice cry "Behold Agnes, Behold!" and fell in. A blind man who came from Knockanure and washed his eyes in the water had his sight restored by the following morning, according to the same tradition. The prescribed ritual involved nine rounds of the well per visit, a rosary said for every three rounds completed, three Hail Marys said in honour of Saint Agnes, and attendance on two particular days: the day after St Patrick's Day and the twenty-ninth of December. The scholar Caoimhín Ó Danachair, writing in 1958, noted the well issuing beneath an old ash tree, and recorded that no devotions were then being observed, a situation that remains the case today.