Neilson, William (Mac Néill, Uilliam) (1774–1821), presbyterian minister, classical and Irish-language scholar and writer, was born 12 September 1774 at Rademon, Kilmore, Co. Down, fourth among seven sons of the Rev. Moses Neilson (1739?–1823), schoolmaster and presbyterian minister of Rademon, and Catherine Neilson (née Welsh). Moses Neilson, who descended from an Ayrshire family, was an impressive scholar in his own right: graduating MA from Glasgow University in 1763, he was fluent in Latin, Greek, Hebrew, and Irish, the language he used to conduct his services. It is likely that the young William Neilson grew up in a household where Irish was used as the first language. He attended the academy that his father had established at Rademon, before attending the University of Glasgow (1789–93), but left without taking a degree. Returning to Ireland, he taught in his father's academy while also taking lessons from Pádraig Ó Loinsigh of Loughinisland, Co. Down, a noted classical and Gaelic scholar. During this period, he also worked for Whitley Stokes (qv), transcribing manuscripts.
In December 1796 he was licensed as a presbyterian minister, and in March 1797 was appointed pastor of the Dundalk congregation. He preached through Irish and used the language for his everyday pastoral work, becoming popular with the predominantly Irish-speaking population of Dundalk. During the 1798 rebellion he was arrested on one occasion while giving a sermon in Irish and was only released when his identity and loyalty had been established. Renowned for his charitable work in the town, he later worked tending those who had been wounded in the rebellion. He established a school at Dundalk which was based on the same lines as his father's. Many of his students, who included Nicholas Joseph Callan (qv), later a priest and noted scientist, and the Young Irelander John O'Hagan (qv), distinguished themselves in their university careers. He did not neglect his own scholarship and in 1804 published Greek exercises in syntax, ellipsis, dialects, prosody and metaphrasis. This work, dedicated to Provost John Kearney (qv) of TCD, had run to eight editions by 1846.
The publication of this work increased his academic reputation considerably, and in 1805 Glasgow University awarded him an honorary DD. He went on a preaching tour of Ulster, delivering his sermons in Irish, and in 1806 was a founding member of the Gaelic Society. His fellow presbyterian ministers were generally supportive of this work and Neilson was elected moderator of the Synod of Ulster (1806). Devoting his spare time to the study of the Irish language, he published Introduction to the Irish language (1808), often referred to simply as ‘Neilson's grammar’, in which he showed himself to be an expert in Irish grammar and morphology, using examples of everyday dialogue to illustrate the nuances of the language. On the basis of his linguistic studies, he was elected MRIA in 1808.
In 1810 he published Greek idioms exhibited in select passages from the best authors and also a short primer for the London Hibernian Society, Cead leabhar na Gaoidheilge. This was the first elementary class book to be published in the Irish language. In his address to the presbyterian synod of 1813, he spoke in favour of catholic emancipation. Appointed professor of classical, Hebrew, and Irish languages at the Belfast Academical Institution in July 1818, he became a prominent member of the Belfast Literary Society, serving as its president 1819–20. He continued to immerse himself in his studies, was a noted collector of Irish manuscripts, and, interested in Irish music, established the Irish Harp Society for the Blind. His last published work was Elementa linguae Graecae (1820). In April 1821 he became ill with rheumatic fever; as he lay on his deathbed, the news was brought to him that he had been elected professor of classics at Glasgow University, succeeding his old friend and mentor, John Young. He died on the night of 26 April 1821. His remains were returned to Rademon to be interred in the family plot; the funeral drew a crowd of over 15,000. He was married; no details are known except that he was survived by a son and daughter.
While much of Neilson's work was later superseded by Irish scholars such as Douglas Hyde (qv) and Eoin MacNeill (qv), he had engaged in pioneering work and did much to rekindle scholarly interest in the Irish language. A collection of his manuscripts is in the NLI, and includes his unpublished commentary on the English–Irish dictionary of Begley and MacCurtin (qv) (1732). In 1996 the Linen Hall Library in Belfast published a facsimile edition of his Introduction to the Irish language.
More information on this entry is available at the National Database of Irish-language biographies (Ainm.ie).