The O'Clery Book of Genealogies, also known as Royal Irish Academy Ms. 23 D 17, was written by Cú Choigcríche Ó Cléirigh, one of the Four Masters, who was transported in the 1650s to Ballyacroy, County Mayo, "under the guidance of Rory O'Donnell, son of Col. Manus O'Donnell, slain at Benburb, 1646."
Upon his death in 1664, he willed his books and manuscripts to his sons, Diarmaid and Sean.
He brought with him manuscripts of Leabhar Gabhala, the O'Clery Book of Genealogies, the Life of Hugh Roe O'Donnell and the [topographical] poems of Seán Mór Ó Dubhagáin (died 1372) and Giolla na Naomh Ó hUidhrín (d. 1420), all written by Cú Choigcríche.
They were purchased by the Royal Irish Academy in November 1829, and remain in their possession.
David Sellar, who was the Lord Lyon King of Arms in Scotland, concluded that it dates from the mid 17th century.