Leath Cuinn and Leath Moga

Leath Cuinn (Conn's Half) and Leath Moga (Mug's half) are legendary ancient divisions of Ireland, respectively north and south of a line corresponding to the Esker Riada running east–west from Dublin Bay to Galway Bay. The eponymous Conn and Mug were Conn Cétchathach (Conn of the Hundred Battles) and Éogan Mór Mug Nuadat (the Servant of Nuada), whose armies in 123 AD fought the battle of Mag Lena (the Plain of Lena, in what is now County Offaly between Tullamore and Durrow).