The name gives away part of the story: Tobar an Duibh, the Well of the Black, takes its name from a dark sediment that accumulates at the base of the water. That sediment was not merely incidental. Local tradition held it useful for dyeing wool and for treating swellings of the eyes and limbs, giving the site a practical, almost medicinal character distinct from the more devotional associations of the typical holy well.

The name appears on the Ordnance Survey six-inch maps of both 1840 and 1916, and a letter written for the OS in 1839 records the well under the Irish form Tobbar Duibh in the townland of Cahirfodda. It was the scholar and antiquary John O'Donovan who noted the curative reputation while also raising a sceptical eyebrow, questioning whether the well had any genuine claim to the designation holy. His hesitation is interesting precisely because it was so unusual; O'Donovan was surveying a landscape thick with wells carrying unambiguous religious associations, and something about this one gave him pause. By the time a physical inspection was carried out in 1997, the site appeared most likely to be a natural spring rather than a constructed or formally venerated feature. It sits in a hollow of exposed limestone pavement, the kind of karst terrain the Burren is known for, with low cliffs of roughly two to five metres rising to the east and north, and two groups of bushes growing near the cliff face to the north.