Drennan
Drennan is a surname of Irish origin and is derived from the Gaelic Ó Droighneáin, Ó Draighnáin, or Ua Draighnen, meaning "descendant of Draighnen", or "descendant of blackthorn". Variant spellings include Drennen, Drenning, Drennon, Drinan, Drinnan, Drinnon, and Drynan. Thornton is another Anglicized surname from the same original Gaelic form. Background. The Uí Draighnáins, a descendant clan of the dynasty of Uí Maine, specifically claiming descent from Cú Connacht mac Dundach of the Síol Anmchadha branch, were chiefs of the country lying around Sliabh Eisi, on the borders of County Clare and Galway. They were formerly hereditary chief Brehons  or judges of the principalities of Hy-Many and Hy-Fiachra Aidhne, in South Connacht, and had their chief residence at a place called Ard-na-Cno, in the parish of Killiny, and barony of Kiltartan, as we are informed in the Book of Lecan: "To the Aes Brengair belongs the stewardship of the arch-chief of Hy-Many, and it is the office of the Ui-Draighnen to distribute justice to the tribes." According to statistics cited by Patrick Hanks, 1,113 people on the island of Great Britain and 592 on the island of Ireland bore the surname Drennan  in 2011. In 1881 there were 404 people with the surname in Great Britain, primarily at Renfrewshire, Ayrshire, Lanarkshire, and Lancashire. In mid-19th-century Ireland, people with the surname Drennan were found mainly at County Laois and County Kilkenny. The 2010 United States Census found 4,233 people with the surname Drenna, making it the 7,821st-most-common name in the country. This represented an increase in absolute numbers, but a decrease in relative frequency, from 3,927 (7,811th-most-common) in the 2000 Census.