These enclosures, known in Irish as raths, were the most common form of rural settlement in Ireland from roughly the fifth to the twelfth century. A rath typically consisted of one or more banks of earth, sometimes topped with a timber palisade, enclosing a family's dwelling and perhaps a small number of outbuildings. Tens of thousands once existed across the island; a few thousand survive in recognisable form today.

The name Foilrim itself has the quality of a place that has largely escaped the documentary record, which is not unusual for townlands in the west of Ireland, where the texture of daily life in the early medieval period tends to be legible only through archaeology rather than written sources. Clare as a county contains a considerable density of ringforts, a reflection of the relatively good preservation of earthworks in areas where later intensive ploughing has been less destructive than in parts of Leinster or Munster. The rath at Foilrim belongs to that broader pattern, a faint circular signature pressed into the ground by people who farmed and lived here well over a thousand years ago.