The town takes its name from the IrishLiosDúinBhearnameaning the "liosdúin", or
enclosured fort, of the gap ("bhearna"). It is believed that the fort
referred to in this name is the green earthen fort of Lissateeaun (fort of the
fairy hill), which lies 3 km to the north-east of the town, near the
remains of a Norman-era castle.
