Traidisiún Gaelach an Leabhair Mhóir / The Gaelic Tradition of the Great Book
In the 21st century, Nollaig Ó Múraíle gave the name "The Great Book of Genealogies" to Dubhaltach Mac Fhir Bhisigh's 17th century Leabhar na nGenealach / Book of Genealogies because it's so big compared to the others which survive, like Ó Cléirigh's Leabhar na nGenealach / Book of Genealogies. But that's just the point - survival. Even though Dubhaltach's book is so much bigger than Ó Cléirigh's, Dubhaltach didn't call his work great or big. Like Ó Cléirigh, he was used to big books and 'great' books (deemed great in Gaelic tradition), working as he did in his family's library and in the libraries of the other learned families which were filled with hundreds or thousands of big and 'great' books which do not survive today.
Leabharlann na Mac Fhirbhisigh / The Mac Fhirbhisigh Family Library
Leabhar Mór Mhic Fhirbhisigh Leacain / The Great Book of Mac Fhirbhisigh of Leacan is one of the genealogical books from Dubhaltach's family library which was already deemed 'great' in Gaelic tradition by the time that Dubhaltach worked with it. It was compiled between 1397 and 1418 by Giolla Íosa Mór Mac Fir Bhisigh with help from Ádhamh Ó Cuirnín and Murchadh Riabhach Ó Cuindlis. It was Dubhaltach's undertaking to update that great work by 250 years of genealogies for all of Ireland!!! The amount of learning, including memorized learning, which it took to create those books, those libraries, and to keep them updated is incredible (using the original sense of the word) by today's standards. And this work in every generation involved considerable physical hardship. For example, Dubhaltach travelled the country during Cromwell's campaigns and famines in order to access other books in other families' libraries and so bring his book up to date, ca. 1650.
Bhris na Mic Fhirbhisigh an Gheis / The Mac Fhirbhisigh Family Broke the Taboo
There's one other reason to praise the Mac Fhirbhisigh learned family. They emphatically refused (unlike Ó Cléirigh and all the other learned families whose genealogical works survive) to abide by the prohibition / taboo against recording the genealogies of the families of the daorchlanna (unfree clans / tribute-paying clans). Wherever and whenever possible, the Mac Fhirbhisigh family noted the existence of those families and clans and provided whatever information survived about their ancestry, however little was left as a result of that prohibition. That's another reason why the Mac Fhir Bhisigh books are bigger, and truly greater.
Le gach dea-ghuí / Best,
Gearóid / Jerry