Connellan, Thaddeus (‘Thady’) (Tadhg Ó Coinnialláin) (c.1780–1854), Irish-language scholar and scribe, was born at Corkhill, Templeboy, Co. Sligo. Little is known of his education except that he received instruction in the classics at a hedge school in Co. Clare. He returned home around 1800 to open a school in Corkhill, which was initially successful but failed after about seven or eight years. Although raised as a catholic, by 1807 he had come under the influence of the teachings of Albert Blest, a baptist, who had been appointed to the Sligo area by the London Hibernian Society. He subsequently converted to protestantism and, with the help of Blest, secured a teaching post in the Hibernian Society's school in Coolaney, Co. Sligo. Ill suited to his new post, he was unable to control his classes, and transferred to a position as organiser for the society, taking up responsibility for training teachers, founding new schools, and the publication of pamphlets. He claimed to have put 100,000 copies of his own pamphlets into circulation. On the foundation of the Irish Society in 1818 he worked fervently to convert his fellow countrymen through the medium of Irish, and collected monies for that purpose while teaching in England during the 1820s. He believed that the best way for Irish people to learn to read English was first to teach them how to read in Irish.
A prolific writer and a competent Irish-language scholar, Connellan published a number of works on religious and linguistic subjects in Irish. He was put in contact with Edward Bunting (qv) by Blest and the two men met during Bunting's visit to Sligo in September 1808. Connellan's publications – mostly translations of scripture and language teaching aids – include: An English–Irish dictionary intended for the use of schools (1814); The two first books of the Pentateuch, or Book of Moses: as a preparation for learners to read the holy scriptures (1814); an Irish-language primer, Teagmhuiseach nó Primér ann a bhfuil ceithre mhíle focal clodhbhuailte déinstiolla do fhréimhbhriathraibh gaodhalacha le mbrigh a saicsbhéarla: maille le roinn dfhoirsgéaluibh Easoip a ngaoidheilge (1815); An Teoluidhe Gaóidheilge lé na bhrigh a Saicsbhearla: intended to assist the native Irish in learning English, through the medium of the Irish Language (1824); and St Matthew's gospel and the Acts of the Apostles, An Soisgeul Do réir Naomh Mata: Gníomhartha na nabscal do léightheoir (1827). He also published Reidh-leighion air ghnothuibh cearba (1835), a translation of Easy lessons in money matters (1835) by Richard Whately (qv). Connellan's interest in the ‘fiannaíocht’ ballad tradition is reflected in two volumes of Irish poetry: Reliques of Irish poetry (1825), containing the Irish texts of some of the poems and songs published in translation by Charlotte Brooke (qv); and An Duanaire(Fiannaigheacht) (1829). Also in 1829 he published a collection of Irish melodies entitled An Duanaire(Fonna Seanma). Connellan's translation also included four poems aimed at encouraging reading in Irish: ‘B'aoibhinn bheith i mBinn Éadair’, ‘Sé an t-each bán an t-aileach aoibhinn luath’, ‘Iomdha sgaith is faith sa Mhumhain’, and ‘Inis fa réim i gcéin san iarthar tá’.
Connellan spent the final years of his life living with his nephew in the parish of Skreen, Co. Sligo, and died 27 July 1854. He wished to be buried with his parents in Templeboy but his family decided that it would be better to bury him in the protestant graveyard in Skreen. There were unruly scenes at the funeral and according to the parish rector, the Rev. Edward Nangle (qv), the funeral goers, who were drunk, put the corpse into the grave and tried to prevent him from reading the service; he claimed to have heard them say ‘Ashes to ashes, dust to dust, if God does not take him, the devil must.’ The case came before the court on 5 October of that year, when evidence was given against five people, three of whom were related to Connellan. Connellan's portrait was painted by James Northcote RA, and hangs in the NGI.