Tobernacoagh, in the townland of Earlspark in County Galway, carries within it the Irish word tobar, meaning a well, most likely a holy well of the kind that appear in their hundreds across Ireland, each one tied to a local saint, a pattern day, a tradition of votive offering, or a belief in curative waters. Holy wells occupy a peculiar place in the Irish landscape, neither fully pre-Christian nor fully Catholic, but something that absorbed elements of both over many centuries, becoming sites of quiet, persistent devotion long after the formal religious structures around them shifted or disappeared entirely.

Beyond the name and its probable meaning, the historical record for this particular site is, at present, thin. What can be said is that Earlspark is a Galway townland, and that the well was considered significant enough to be recorded as a monument in its own right, placed alongside ringforts, souterrains, and other remnants of earlier habitation that pepper this part of Connacht. The second element of the name, nacoagh, may derive from the Irish an chuach, meaning the cuckoo, though place-name etymology in Ireland is rarely straightforward and alternative readings are possible. A well named for the cuckoo would not be unusual in a landscape where seasonal associations, bird calls, and the rhythms of the farming year were woven into the naming of natural features for generations.