Tullylish Parish, in Irish "Tulach Lis" meaning `the hill of the fort' or, as stated by Dr. R. Ivens, `the hill of the enclosure', owes its origin to the siting of an early monastery on an elevated hill overlooking the River Bann to the east of the present Church of Ireland in the townland of Tullylish.

That a fort, and later a monastery, should be sited here is understandable since it was a feature of early Celtic raths and monasteries that they should be situated convenient to a line of communication and close to a river. To state when the monastery at Tullylish was established is not possible but it may be presumed it was founded in the 6th. or 7th. Century.

In the Annals of Ulster we find a record of the killing of Abbot Dunchu in the year 804 near the shrine of St. Patrick in `Tulach-Lois’, which the author identifies with Tullylish in Iveagh. If that is so, then the existence here at that period of a shrine of St. Patrick is of immense interest. The presence of an abbot is a clear indication that a monastery had been here for some time before the killing. Dr. Anne Hamlin, a noted authority on early Celtic Monasticism, states that the killing is the only one of the period ever to be recorded; unfortunately for us, the reason for such a crime is not given.

However, it seems unlikely that Tullylish was established before the monastery in Dromore, which was founded by St. Colman about 510 A.D. The fact that Tullylish monastery was enclosed in a circular fort or rath-like structure is an indication that it occupied a former Celtic site, which was defensive in nature. Another monastic site in the parish is found in Donacloney, in the old churchyard, on the banks of the River Lagan.