There are several variations on the name Carroll but the definitive statement is considered to be "Gilberts 'National Mss of Ireland' Part III xxx B" which states:
As several more or less erroneous derivations for the name are commonly given, it may be well to state the correct one on no less an authority than "King Cormac's Glossary" viz-
"cerball (carroll) signifies a warlike champion"
the last syllable being etymologically akin to the Latin bellum.
There were in fact several different septs (clans) of Carrolls. The O'Carrolls of Ely O'Carroll and Oriel were major septs while there were minor septs in Kerry and Leitrim. There were also two Mac Carroll septs, one an Ulster sept noted for its musicians, the other in South Leinster.
The descendants of Taig and the Eberian Kings who were to become the O'Carrolls settled in Ely. This was a territory between Lough Derg on the river Shannon and the Slieve Bloom mountains. The territory consisted of Lower Ormond and the Ikerrin in north Tipperary together with Clanrisk and Ballybritt in south Offaly.
The Éile, the Iron Age tribal group from which the Ui Chearbhaill emerged, are immortalised in the ancient place name Bri Éile, now Croghan Hill in north County Offaly, and Moin Éile, the 'Notorious Red Bog of Ely' as Sir William Petty and his wary surveyors described it in 1657. In addition, Cnoc Sidhe Una, the hill of Knockshegowna, County Tipperary, used in the past as an assembly site during the festival of Lughnasa, has always been associated with the fairy queen Una, guardian of the O'Carroll dynasts of Ely. Moreover, a number of spring wells in the territory have the name Tobercarroll, one of the heights in the Sliabh Bloom mountain range is called Carroll's Hill, and a peculiar circular enclosure in the townland of Ballinree on the Birr Estate is known as O'Carroll's Ring.
The O'Carrolls were a formidable, and for some time invincible, Gaelic aristocratic family who ruled the 'eight tuatha' which constituted the territory of Éile.
It was not, however, until the eleventh century that family names as we now know them came into general use in Ireland. They were originally intended to perpetuate the name of some great man whom his descendants were proud to claim as an ancestor.
The patronymic 'O' meaning 'descendant of' or 'Mac' meaning 'son of' and the compound was then handed down from father to son as a family name.
The Carroll (or warlike champion) from whom the patronymic is derived was Maoniugh who led the Elians at the battle of Clontarf which was fought on Good Friday in the year 1014.
The battle of Clontarf was fought, outside Dublin, between the Irish under Brian Boru and the Danes under Sitric. Both armies were estimated at around 20,000 men but the Danes were said to be the better armed. The battle lasted for one cold, windy day until eventually the Danes were driven back to the beach at Clontarf, where an exceptionally high tide drowned thousands of them before they could reach the safety of their ships.
This battle represented the end to the Viking threat to Ireland and, not only did the Danes embrace the Christian faith, but as the land settled to peace Irish art and architecture enjoyed another renaissance which was to last around a century.
Maoniugh was eventually slain in 1022.
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