Chiefs of the Clan Feargusa, they descended from Fergus Cerrbél mac Conaill Cremthainne (Fergus Crooked Mouth) grandson of Niall of the Nine Hostages said to be High King of Ireland from 370 to 406 who in turn descends from Conn of the Hundred Battles the Milesian Gaelic King of Tara / Ireland in the 2nd century.
For over six hundred years the O'Hagans were hereditary brehons and inaugurators of O'Neill (surname) who were descended from the Uí Néill.
O'Hagans are one of the oldest families in Omeath Co.Louth, arrived when O'Neill attacked Mountjoy at narrowwater on his journey to Carlingford.
During the 17th century O'Hagans staunchly opposed English aggression and a number were at the Battle of Kinsale in 1603, suffering great losses with the dispossessions that followed.
Bernard Anthony O'Hagan [Tony] Lecturer Sinn Fein counciller Mid Ulster (b 12/9/1953 -16/9/1991) Murdered.