fifth-century Church of Saint Brecan. A ringfort on Inisheer, called Dún Formna, became the site of a castle built by the O'Briens around the 14th century...

points, in the north of Inisheer. A ringfort once stood on the site, named Dún Formna ("hillfort of the ridge/shoulder", referring to the "shoulder" of land)...

than the other Aran Islands forts like Dún Conor, and perhaps contemporary with Dún Formna on Inisheer. The name Dún Mur is believed to have the same derivation...

to the Annals of Innisfallen, which represents a Munster perspective, "formna Gall herend" ('the best part of the foreigners of Ireland') fell therein...