ODomhnaill

O'Domhnaill is an Irish surname. It is an anglicized form of the Gaelic Ó Domhnaill, meaning "descendant of Domhnall". The personal name Domhnall is believed to derive from the elements "domhan" (world) and "val" (great), thus meaning "great ruler" or "world ruler". This name was borne by several historical figures of importance in Ireland.

The O'Domhnaill clan was one of the most powerful Gaelic dynasties in medieval Ireland. They were primarily associated with the province of Ulster, particularly with the region known as Tyrconnell (Tír Chonaill), which is roughly equivalent to modern County Donegal. For centuries, the O'Domhnaills were the ruling family of Tyrconnell, and they played a significant role in the political and military landscape of Ireland, often clashing with other powerful clans and English forces.

Prominent members of the O'Domhnaill family include chieftains and military leaders who resisted English expansion. The surname is still common in Ireland and among the Irish diaspora worldwide, particularly in countries such as the United States, Canada, Australia, and the United Kingdom. Variations in spelling can occur due to historical anglicization processes.