According to a theory advanced by
T. F. O'Rahilly, the traditional story of the Three Collas is not historical, although it has a basis in history. O'Rahilly argues that the breaking of the power of the Ulaid, the destruction of Emain Macha and the establishment of the kingdoms of the Airgialla were actually accomplished by the three sons of
Niall Noígiallach,
Conall, Endae and
Eógan, who established the kingdoms of Tir Eógan and Tir Conaill in north-western Ulster in the mid-5th century. He believes the Three Collas are literary doublets of the three sons of Niall, their story a genealogical fiction intended to give the tributary kingdoms of the Airgialla a noble pedigree. This theory is followed by more recent historians, including
Francis J. Byrne, and
Dáibhí Ó Cróinín. Donald Schlegel claims the brothers' tripartite names to be the only examples in ancient Ireland of brothers using the Roman style naming convention of personal name followed by family name followed by an epithet. This may reflect their alleged "return" from exile in
Alba, which at the traditional time of their story—the 4th-century—was part of the
Roman Empire. Schlegel suggests that being put in command of 300 soldiers may have meant that were centurions in the Roman army. Schlegel also argues that the Three Collas, along with their name "Colla", may have descended from the
Trinovantes of Britain. He claims that Trinovantes mistranslated by
Ollams into Irish could have produced the name
Airgíalla, the name given to the territory the Three Collas conquered in Ulster. In regards to Colla, it may derive from the names Coill or Coel, both of which
Geoffrey Keating mentioned in the area the Trinovantes lived,
Camulodunum (modern-day
Colchester). ==Family tree==