An enclosure, the kind of roughly circular earthwork that would once have defined a farmstead or settlement boundary in early medieval Ireland, was recorded clearly enough on the Ordnance Survey's six-inch map of 1846. By the time surveyors returned to update that map in 1892, it was gone, levelled at some point in the intervening decades, most likely cleared to make way for agricultural improvement.

What the 1846 map captured was a feature that had probably stood for many centuries before that moment of recording. Enclosures of this type, sometimes called raths or ringforts depending on their construction, were built in their thousands across Ireland during the early medieval period, serving as enclosed farmsteads for families and their livestock. Many were dismantled during the land clearances and drainage schemes of the nineteenth century, particularly in the decades surrounding and following the Famine, when landlords and tenants alike reshaped the countryside with new urgency. The Tonavane enclosure fits that pattern almost exactly. A field inspection carried out after the 1892 map was published found no visible structural remains, though surveyors noted undulations in the ground, slight rises and dips that mark where the earthwork once sat.