Recorded in the spellings of O'Beirne and Beirne, this is an Irish surname. It is claimed by eminent authorities that although it is pronounced exactly the same as more familiar O'Byrne, the two clans are totally separate. O'Beirne being originally from County Roscommon and O'Byrne from County Kildare, although for the past eight hundred years South Wicklow has been their home. This may be so but it would take some proving. What is certain is that the O'Beirnes have long been associated with the clan MacDermot, and in the 13th century they combined to drive the O'Monahans out of the territory known as Tir Bruin, near Jamestown, on the Roscommon side of the Shannon. It is said that as recently as 1850 they still held significants lands in that region. Surprisingly few members of the clan have had any lasting impression on Irish history, but many went to France where they flourished as priests. Amongst these was Thomas O'Beirne who though reared a Roman Catholic and it is said attended the Catholic seminary at Douai, committed the ultimate sin of becoming not only a protestant, but eventually the Bishop of Meath in 1789! Another character was Henry O'Beirne who emigrated to America in about 1815. He became one of the leading authorities on the native population, and in particular the Texas Indians, with whom he lived permanently until his death in 1851.