The Ó Fearghuis were themselves Irish nobility for descent from King Niall, originally based at Roscam, in Clann Fhergail.
The Liber Flavus Fergusiorum was composed at various times by several different scribes of the Ó Fearghuis, the principal one identifying himself as Aedh.
Two translators, Seaán Ó Conchubair and Uidhisdín Mag Raighin, are named in colophons.
The book derives its name from the Ó Fearghuis family, whose descendant Dr. John Fergus brought the manuscript from County Mayo to Dublin in the 18th century.
Upon his death in 1761, it was held by his daughter, Frances Arabella Kennedy, whose grandson deposited it in the Royal Irish Academy in 1875.