Bermingham, Peter (d. 1308), lord of Tethmoy and Dunmore, was a son of James de Bermingham and the grandson of Peter de Bermingham (qv) (d. 1254). This second Peter, who features in the record from 1283, when he visited England, was a vassal of John fitz Thomas FitzGerald (qv), from whom he held Tethmoy and to whom he swore fealty in 1289; this deed is one of the earliest lifetime contracts surviving in Britain and Ireland. In the same year Peter, who was under pressure from the Gaelic ruling lineage of Uí Failge, was defeated by An Calbach O’Connor Faly (qv). Peter's relationships with his Irish neighbours did not improve; ten years later he is known to have been provided with four hundred footmen for the defence of the marchlands.
Peter married Ela, a daughter of William de Oddingeseles, who was justiciar of Ireland in 1294–5. Up to this time he had still claimed lands in Tireragh, but in 1297 he conceded these to his cousins the Poers. Another cousin was Meiler's son, known as Peter of Athenry, who was slain on the plain of Connacht in 1309. Bermingham, was summoned on several occasions to aid Edward I in his wars. In 1294 he was on campaign in Gascony; in 1296 and again in 1301 he fought in Scotland. It may in part have been his absences abroad that encouraged the Irish of the marchlands to press their claims at his expense.
In 1305, perhaps in an effort to secure his own lordship, Peter was responsible for the elimination of several Uí Failge dynasts in circumstances which, according to the Irish annals, savoured of treachery. In his defence, Orpen cites an elegy, the remarkable Middle English poem about Bermingham, one of the ‘Kildare poems’ (BL, Harley MS 913), which implies that the Uí Failge had conspired against the settlers. Whoever was to blame, however, the outcome was that Calbach, Muirchertach (qv), and Máelmórda Ó Conchobair, among others, were slain at the castle of Carrick in Carbury. The Laud Annals may well be correct in claiming that Jordan Comyn actually carried out the killings, but the justiciary rolls make it clear that Peter Bermingham was rewarded with £100 from the treasury. This massacre is one of the episodes referred to in the remonstrance addressed to Pope John XXII in the name of Domnall Ó Néill (qv), king of Ulster. The killing of the Uí Failge dynasts sparked off a renewal of the tit-for-tat marcher warfare that had marked the 1290s, but Peter was on the whole successful in retaining control of the colonised districts.
Peter Bermingham died on Easter Saturday 1308 and was buried at the Franciscan friary in Kildare. He was succeeded in the lordship of Tethmoy by his son John Bermingham (qv).