The great Connacht scholar Dubhaltach Mac Fhirbhisigh (c.1600-1671), from Lackan, Co. Sligo, compiled his monumental Great Book of Genealogies in Galway at the height of the Cromwellian Wars in the mid-seventeenth century. The work has long been recognised as the most important source for the study of Irish family history, and it is also of great importance to historians of pre-17th century Ireland since it details the ancestry of many significant figures in Irish history - including: Brian Boroimhe (d.1014); Ulick Burke, Marquis of Clanricarde (d.1657); James Butler, Duke of Ormonde (d.1688); Somhairle Buidhe (Sorley Boy) MacDonnell (d.1589); Randal MacDonnell, Marquis of Antrim (d.1683); Garrett Og Fitzgerald, Earl of Kildare (d.1536); Diarmuid Mac Murchadha (d.1171); Myler Magrath, Archbishop of Cashel (d.1622), Murrough O'Brien, Baron of Inchiquin (d.1674); Feagh MacHugh O'Byrne (d.1597); Rory O'Conor.(d.1198); Red Hugh O'Donnell (d.1602); Hugh O'Neill, Earl of Tyrone (d.1616); Owen Roe O'Neill (d.1649), and many, many more.
The Great Book of Genealogies, is a five volume set of over 3100 pages. It is a fantastic asset to historians of Irish History and an amazing piece of work. It has been translated by Nollaig O Muraile with accompanying indicies.