The story goes like this-
Long ago, during the 17th century, the O’Neills and O’Reillys were two revolutionary Irish families. They formed a rowing competition to reserve rights to some highly regarded land. The two rowing teams agreed that the first to touch the land would have their choice of the land on the other side. The youngest sibling on the O'Reilly boat didn't want to miss out on this opportunity, so he grabbed his own sword, cut off his hand and threw it ashore. He ruled over County Cavan and this land still remains in the O'Reilly family.