The below article was written for a scholarly journal in 1918 by Gustavus E. Hamilton, regarding the origins of the name Kilcoole. This journal has been scanned and is available online.
The Journal of the Royal Society of Antiquaries of Ireland
Vol. XLVII / Volume 47 (Consecutive Series), Vol. VII / Volume 7 (Sixth Series) 1917
Kilcoole, Co. Wicklow: its Name.—This name is usually interpreted as Cill Chuile, the church of the corner or recess, but this interpretation is incorrect. It is really Cill Chomhghaill, Comhghall’s church. In a letter of Pope Alexander III, dated A.D. 1179, and written to Labhras O Tuathail, Archbishop of Dublin, confirming to him and his successors possession of the See with metropolitan jurisdiction over the dioceses of Glendaloch, &c., the churches of “Rathmichael, Cellcomgaill, Cellachaith Driegnic” are mentioned. In the letter of Pope Innocent III, dated in A.D. 1216, the names are “Killadreni, Kilcohul, Glendelach.” In King John’s confirmation to John Comyn, Archbishop of Dublin, given when he was Count of Moreton and “Dominus Hiberniae,” and therefore before A.D. 1199, the names are “Killadreini, Kilkoel, Rathmichael.” In the list of churches in the diocese of Dublin compiled in the time of Archbishop Henri de Loundres (A.D. 1212-1228), the following churches are given in the deanery of “Bree”—“Ecclesia de Killauchdeeny, Ecclesia de Kilcowyl.”
Dr. Joyce was correct in his interpretation of Kilcoole. O Donovan wrongly identified Kilcoole with the Cill Chuile Dumha, where Bran Airdceann, King of Leinster, and his wife were buried by his grandnephew, Fionnachta Ceirderg, which the Leabhar Laighean tells us was in Laoighis Chuile, which was in Magh Reata, now Morett, in the parish of Coolbanagher, and barony of Portnahinch, Queen’s County.
Gustavus E. Hamilton, M.R.I.A.
 Gilbert, Crede Mihi, p. 2.
 Ibid., p. 9.
 Ibid., p. 37.
 Ibid., p. 142
 Irish Names of Places, iii, 406.
 Annals of the Four Masters, i. 396.
 Leabhar Laighean, 39b; MacFirbhisigh’s Leabhar Geinealach, 426.
 Leabhar Geinealach, 556.