Their territory was called Cuil-na-n-Oirear, i.e. the corner or angle of harbours, situated on the eastern shore of Upper Lough Erne, immediately opposite some beautiful islets, whose indentations form the miniature haven that gave the place its title.
It became known as the barony of Coole.
The Úa Caiside were hereditary doctors in medicine, or state physicians of the Maguires, the former chiefs of Fermanagh; and they held their district ex officio, according to the laws of tanistry.
In 1541, Roderick Cassidy, Archdeacon of Clogher, eminently versed in the historical records of his country, died.
Besides having written part of the Register of Clogher, he also compiled the latter part of the Annals of Ulster.
Among inquisitions in the Exchequer is one taken at Ballycassidy, County Fermanagh, in 1630, at which time the family had branched out widely in the counties of Fermanagh, Louth, and Monaghan.
To one of these scions we refer
HENRY O'CASSIDY MD, who had followed his ancestral pursuits in medicine, was of Greatwood, Mullaghbawn, and Drumkirk, County Louth, and of various estates in County Monaghan.
He was born ca 1650.
Dr O'Cassidy married and had issue, with others,
FERGUS, his heir;The elder son,
Edmund, scholar of Trinity College, Dublin, in 1710;
Margaret, m Eugene O'Docherty, of Newtown, County Leitrim.
FERGUS O'CASSIDY, of Greatwood, County Louth, and of "Derry", County Monaghan, had two sons, of whom the elder,
PATRICK CASSIDY, of Derry, in the parish of Magheracloone, near Carrickmacross, espoused Catherine Flood, and had issue.
Mr Cassidy's last will was dated 1753, and proved in 1757.
Among other directions he desired "to be buried in my tombe at Carrick McCross".
His youngest son,
FRANCIS CASSIDY, born ca 1747, of Cashel, County Tipperary, wedded Sarah Magee, a first cousin of the Most Rev William Magee, Lord Archbishop of Dublin, and had issue,
MARK, his heir;His eldest son,
Francis Duff, captain, 60th Rifles, private secretary to Lord Castlereagh, the statesman;
Francis, who died young.
THE REV MARK CASSIDY (1777-1839), scholar of Trinity College, Dublin, 1797; chancellor of Kilfenora, and incumbent of Newtownards, County Down, ca 1808-39.
He married, in 1808, Henrietta, daughter and co-heiress with her sister Esther, wife of the Rev Prebendary Cleland, of Samuel Jackson, of Stormount [sic], near Belfast, a West Indian planter.
Mr Cassidy had issue,
Samuel, of Glenbrook, Co Londonderry; m Esther Scott; d childless, 1843;Mr Cassidy's second son,
FRANCIS PETER, of whom presently;
Frederick (Rev), vicar of Grindon, Co Durham;
Robert, LL.D., of Ballyhackamore House, Belfast, m Anne, daughter of Dr Ardagh;
Loftus Tottenham, lieutenant-colonel, 18th Hussars;
Sarah; Henrietta; Fanny; Emily.
FRANCIS PETER CASSIDY JP, of Glenbrook, County Londonderry, a colonel in the 34th Regiment, married, in 1853, Maria Lucy Anne, daughter of Matthew Hayman, of South Abbey, Youghal, and had issue,
FRANCIS RICHARD, his heir;Colonel Cassidy served with his regiment during the Indian mutiny, and was severely wounded at the battle of Cawnpore, in 1857.
Helen Hayman Henrietta;
Dying in 1859, he was succeeded by his eldest son,
FRANCIS RICHARD CASSIDI MBE JP MD (1858-1939), of Glenbrook, Director of Transport, First Line Hospitals, Derbyshire, in 1st World War; Associate of the Order of St John of Jerusalem.
Dr Cassidi wedded, in 1887, Marion Elizabeth, daughter of Dr John Duncanson, of Alloa, Clackmannanshire, and had issue,
FRANCIS LAIRD, b 1889;The elder son,
Robert Alexander, Lt-Cdr, RN; b 1894;
Marjorie May, 1888-90.
FRANCIS LAIRD CASSIDI VRD MB (1889-1963), of Glenbrook (which property he made over to his son, 1950); surgeon captain, RNVR; honorary surgeon to HM King GEORGE VI.
Dr Cassidi married, in 1924, Phyllis Mary, daughter of the Rev A C Haviland, of Lilley Rectory, Hertfordshire, and had issue,
FRANCIS PAUL, of whom we treat;The only son,
Oonagh Teresa, served during 2nd World War in WRNS;
Catriona Elspeth, b 1955.
FRANCIS PAUL CASSIDI TD MB, of Glenbrook, born in 1925, married, in 1953, Barbara Geraldine, daughter of Major W T Temple RA, of 118 Shorncliffe Road, Folkestone, Kent;
He graduated from St Thomas Hospital Medical School, London, in 1948, with a Bachelor of Surgery; RMO, 4th Battalion, The Buffs (Territorial Army); major, Royal Army Medical Corps (Territorial Army); Police Surgeon, KCC; Medical Officer at HM Prison, Canterbury, Kent; Territorial Decoration, 1968.Dr Cassidi lived, in 1976, at St Dunstan's House, Canterbury, Kent, and at Glenbrook, Magherafelt, County Londonderry, and had issue,
Francis James, b 1962;
Penelope Jenetta, b 1954;
Alison Ruth, b 1955;
Melian Geraldine, b 1959.
GLENBROOK HOUSE, near Magherafelt, County Londonderry, is a somewhat Gothic, late-Georgian house.
Its entrance is in a three-sided, battlemented bow between two gables with finials and small, overhanging oriels.
The house had become neglected and derelict for a period.
It was completely restored and enhanced in 2013 by Des Ewing Architects for the new owner.
First published in November, 2013.