[4][5] The Irish name Maigh Charnáin means "plain of the cairn."

Moycarn barony is located in the south of County Roscommon, north of the River Suck and River Shannon; they meet at the southern tip.

[6] The Moycarn barony was anciently called Clan Laithemhain or Muintir Cionaith, ruled by the Gaelic Irish tribes of MacGilla Finnagain (O'Finnegan) and Ó Cionnaoith (Kenny).

[7] It is referred to in the topographical poem Tuilleadh feasa ar Éirinn óigh (Giolla na Naomh Ó hUidhrín, d. 1420): Mac Giolla Fionnagáin maoiṫ Agus Clann crodha Cionaoith Dá droing ar aoḃḋa d' feadain Ar Cloinn laomḋa Laiṫeaṁain ("Mac Gilla Finnegan the mild and the valiant Clan Kenny: two tribes who are fair so be seen rule over the brave Clan Flahavan.

")[8][9][10][11] Notable later families in the barony include the ffrench and Potts.