The town has been a centre of population since Celtic times, probably because of its elevated position offering a view over the surrounding countryside. It is mentioned in the ancient Irish epic, the Táin Bó Cuailgne, as being one of the places where Queen Medb and her army stopped on their journey to take the Donn Cuailnge (the Brown Bull of Cooley). The name of the town is itself so ancient as to be unclear even in Irish; the 11th-century writers of the Lebor na hUidre (containing the oldest written version of the Táin) refer to it by means of a gloss as ”Gránairud Tethba tuaiscirt .i. Gránard indiu” (”Gránairud of northern Teathbha, i.e. Gránard of today”). According to the Tripartite Life of Saint Patrick, Patrick appointed Guasacht, a son of his former master Milchú, as first bishop of Granard, but the diocese did not survive as a separate entity. The surname Sheridan was first recorded in Granard in the 8th century.