The de Berminghams were a very prominent family in the Norman incursions into Ireland. Robert de Bermingham accompanied Strongbow to Ireland in 1172. The de Berminghams held lands in Kildare and claimed the manor of Kells (winning it in 1346) in which the Erleys were one of the most prominent families. But other members of the de Bermingham family held Athenry and Dundalk. In 1235 Peter de Bermingham accompanied Richard de Burgh on his conquest of Connaught and was created the first lord of Athenry. On the death of the second Richard de Burgh in 1248, Peter was given custody of his lands and castles. Also about this time (1235) Meiler de Bermingham, Peter's son, built a castle at Athenry. In 1249 the Normans defeated a local Irish army under Terlaugh mac Hugh. In 1316 Richard de Bermingham, Lord of Athenry defeated the Irish under Felim O'Connor at the battle of Athenry and in 1395 Walter de Bermingham, Lord of Athenry was knighted by Richard I.

 Piers (Peter) Bermingham was the son of Robert Bermingham.1 He died in 1254. In 1234 he received 20 marks a year from King Henry III. In 1243/44 he was specially thanked (along with 22 of the native chiefs) by the King for his zeal in the King's service. G.E. Cokayne; with Vicary Gibbs, H.A. Doubleday, Geoffrey H. White, Duncan Warrand and Lord Howard de Walden, editors, The Complete Peerage of England, Scotland, Ireland, Great Britain and the United Kingdom, Extant, Extinct or Dormant, new ed., 13 volumes in 14 (1910-1959; reprint in 6 volumes, Gloucester, U.K.: Alan Sutton Publishing, 2000), volume I, page 291.