East Breifne

East Breifne, or Breifne O Reilly, was a Gaelic kingdom roughly corresponding to the later County Cavan. The O Reillys ruled from Tullymongan Hill after Breifne was divided in 1256; Richard was king in 1337.

From the early fifteenth century, Cavan minted silver O Reilly money. English parliaments banned the coins in 1447 and 1456, but trade continued to prosper. The O Reillys joined the Nine Years War; after the 1603 Treaty of Mellifont and the 1607 Flight of the Earls, dozens were attainted and their lands opened to the Plantation of Cavan.