Anderson's maternal grandfather Trevor Bigham was the Deputy Commissioner of the Metropolitan Police from 1914 to 1931. One of Anderson's grandmothers, Lady Frances O'Gorman, belonged to the Gaelic Mac Gormáin clan of County Clare and was the daughter of the Irish Home Rule MP Major Purcell O'Gorman. Major Purcell O'Gorman was in turn the son of Nicholas Purcell O'Gorman who had been involved with the Republican Society of United Irishmen during the 1798 Rising, later becoming Secretary of the Catholic Association in the 1820s. Benedict Anderson took his middle names from the cousin of Major Purcell O'Gorman, Richard O'Gorman, who was one of the leaders of the Young Irelander Rebellion of 1848.