O'Reilly, Edward (1765–1830), Irish scholar, lexicographer, and apothecary, was born 6 December 1765, probably in Harold's Cross, Dublin, although some accounts state he was born in Co. Cavan or Co. Meath. Nothing is known of his parents but according to the Irish Book Lover he was a descendant of the O'Reillys of Breifne and a brother of Andrew O'Reilly (d. 1862), a former United Irishman and the Paris correspondent for The Times. According to Robin Flower (qv), Eoghan O'Reilly of Corstown, Co. Meath was his grandfather. Nothing is known of his education apart from the fact that he did not receive a classical education. His obituary in the National Magazine (October 1830) stated that he spent the early part of his life working in a merchant's office and subsequently in a retail business in order to support a ‘numerous family’.
O'Reilly was considered one of the foremost Irish language scholars of his time and his study of the language is said to have begun after he bought a considerable number of manuscripts and books from a young man named Wright (Enrí Mac an tSaoir) who was about to emigrate. These were originally in the possession of the Gaelic scribe and teacher Muiris Ó Gormáin (qv) and the collection is reported to have filled five large sacks. According to a note in Ó Gormáin's handwriting (BL, MS Eg. 135), O'Reilly had already purchased ‘an ancient manuscript’ from him prior to this. Based on this collection of books and manuscripts, O'Reilly built up his knowledge of the Irish language and is reported to have later refused fifty guineas for one of the manuscripts. O'Reilly transcribed a number of manuscripts (including BL, MS Eg. 154), completed at two different stages in the scholar's life. The second part of the manuscript displays an improvement in both his command of Irish and his penmanship. A comment by the scholar, John O'Donovan (qv), indicates he did not consider O'Reilly's spoken Irish to be of a high standard: ‘This is ascertained from the living voice of people who speak Irish at the present day (which is more authority than O'Reilly who could not pronounce Irish at all)’ (RSAI Jn. (1949), 153).
Together with Edward Farmer, a Co. Cavan schoolmaster, he founded an Irish school in Richmond St., Dublin in 1810. Both men were also active in collecting old country airs and tunes. He was a member of the Ossianic Society in 1817 and his first publication, Sanas Gaoidhilge/Sags–Bhéarla (1817), which he compiled from materials collected by the scholar William Haliday (qv) and to which he appended an Irish grammar, also appeared that year. On its foundation in 1818 he became assistant secretary to the Iberno–Celtic Society, a successor to the Gaelic Society of Dublin; it included several distinguished scholars such as George Petrie (qv), James Hardiman (qv), and Sir William Betham (qv). O'Reilly was also a member of the Record Tower Society in 1819 and is reported to have also considered applying for a professorship in Irish in St Patrick's College, Maynooth. A year later, he published A chronological account of nearly four hundred Irish writers with a descriptive catalogue of their works (1820), the Iberno–Celtic Society's only publication. This work was written in the form of the annals and begins with the Milesian poet, Amergin, and ends with the south Ulster poet Art Mac Cumhaigh (qv). O'Reilly's plans to publish a second volume of anonymous authors never came to fruition. He contributed several articles to the RIA Transactions, including a piece on the brehon laws entitled ‘An essay on the nature and influence of the ancient Irish institutes’ for which he won an award in 1824. Five years later in 1829 he won a further prize from the RIA for his ‘Essay on the authenticity of the poems of Ossian’, published posthumously. It is believed he was responsible for preparing the Hibernian Bible Society's Irish language Bible for publication (1830), for which he received two shillings per page.
H. J. Monck Mason (qv) employed him to catalogue the Irish language manuscripts in case H in the library of TCD but according to E. J. Gwynn (qv), his work was ‘usually superficial and frequently incorrect’ (TCD Catalogue, xix). He seems to have completed his task by 1819 or soon afterwards. O'Reilly was also employed as amanuensis to the Ulster king of arms, Sir William Betham, and assisted him with his genealogical and antiquarian studies.
O'Reilly's health was in decline by the time he began work at the Ordnance Survey of Ireland as an Irish-language advisor. Although he spent only four months working there, from April 1830 until his death in August that year, and received the paltry remuneration of sixpence per page, his work had an important role in setting the study of topography in Ireland on a professional footing. His duties consisted of providing an explanation of toponyms in counties Derry, Donegal, Fermanagh, Tyrone, Meath and Westmeath as well as a ‘revision’ and ‘settling’ of the English orthography. He also compiled information on topographical features and local traditions. He did not conduct any fieldwork but depended on information sent back to Dublin from those working on the ground. John O'Donovan succeeded O'Reilly as Irish language advisor after his death and was often critical of his predecessor's work: ‘O'Reilly seems to be as unfixed in his grammatical principles as the orthography of the names he was elucidating’ (RSAI Jn. (1949), 153).
O'Reilly died 26 August 1830 at his home in Harold's Cross, Dublin. It is believed he left a number of unpublished works, including an English–Irish dictionary, translations of the Annals of Innisfallen, a life of Aodh Rua O'Donnell (qv) and a considerable portion of the Annals of the four masters as well as a projected life of Turlough Carolan (qv) with a collection of the harper's songs and their original melodies. The RIA purchased most of his manuscripts at auction on 30 November 1830. George Petrie bought the O'Clery manuscripts in the collection and later sold them to the RIA at cost price. There are 71 letters concerning the compilation of O'Reilly's dictionary from various of his correspondents in UCD Archives (IE UCDA LA7).