The Toolan surname in Ireland has roots that trace back to the Gaelic name "Ó Tuathaláin," which is derived from "Tuathal," meaning "ruler of the people." The prefix "Ó" signifies "descendant of," indicating that the bearers of this surname were descendants of someone named Tuathal. Originally, this name was associated with the province of Ulster, specifically in the barony of Tirhugh, County Donegal. Over time, the Toolan family, like many Donegal families, migrated to County Mayo, particularly following the O'Donnells in the 17th century. However, some members of the sept remained in their original areas, as evidenced by historical records like the Hearth Money Rolls of 1665. The surname has seen various spellings including Tolan, Toland, and Toolin, suggesting a complex history of anglicization and regional variations. In some regions like Achill, the name took on the form "Thulis." The Toolan name also has connections to religious significance, potentially translating to "the male descendant of the follower of the lord," aligning with many Irish surnames that have religious or holy origins. Additionally, historical records note a Petrus O'Tuathalain serving as vicar of Killaspugbrone in County Sligo in 1306, indicating the presence of the Toolan name in different parts of Ireland over centuries. The variations and migrations of the Toolan name reflect not only the historical movements and anglicization of Irish surnames but also the cultural and political changes that influenced family names in Ireland