Cúill

Cúill is a surname of Irish origin. It is an anglicized form of the Gaelic surname Ó Cuill. The prefix "Ó" signifies "descendant of," and "Cuill" is believed to be derived from the personal name Cuill, which may mean "hazel" or "hewer." The surname is most commonly found in the province of Ulster, particularly in counties Donegal, Tyrone, and Derry.

Historically, families bearing the Ó Cuill surname were associated with various regions within Ulster. The name's distribution suggests a lineage that may have spread from a common ancestor. Like many Irish surnames, its prevalence has shifted over centuries due to emigration and population changes. Today, Cúill and its variations can be found not only in Ireland but also in countries with significant Irish diaspora, such as the United States, Canada, Australia, and the United Kingdom. The surname does not have a specific heraldic crest associated with all branches, as armorial bearings were often specific to individual septs or families within the larger clan structure.