Rams is mentioned in the Annals of the Four Masters. Cumaighe, son of Deoraidh Ua Floinn, lord of Durlas, was drowned in Loch-Eathach (Lough Neagh), after the island of Inis-Draicrenn (Rams Island) had been taken by the Ui-Eatach, where forty-four persons were slain.
Derlas (Derlus, Durlais) - The location for a t​​erritory named Derlus is described by John O'Donavan in Ui Tuitre, co. Antrim.
As the Ua Floinn (or O'Lynn) are described as chiefs of Durlas in the 12th & 13th centuries, and McLysaght places them in southern Armagh (between Lough Neagh and the sea), perhaps the country of Derlas was on the Armagh-Down border. McLysaght cites the Ua Floinn lineage from Clanna Rury of Ulidia, tracing their descent Colla Uais.

Since the reference in the Annals for 'Inis Darcarcrenn' seems to be Ram's Island, near the eastern shore of Lough Neagh, the location of Derlas was likely in county Antrim. The Ui Tuitre of co. Derry are known to have moved west across the river Bann, into county Antrim, supplanting the lands of the Eilne branch of the Dal nAraide by the 10th century. Ua Floinn (O'Flynn, O'Lynn) were Ui Tuirtre leaders as were the later kings of Derlas.

The origins of its present name are largely surrounded by speculation. The earliest known name was Inis-Draicrenn/ Inis Darcarcrenn, and by the seventeenth century this had been anglicised to Ems/Enis Garden. The present name may have derived from the ending "raicrenn" of the original name being confused in pronunciation with the Gaelic word "reithe" meaning a "ram". Speed's map of Ulster, dated 1610, and Johan Blaue's map of 1654, both mark the island as "Enis Garden" and show the symbol of a church tower. It is on record that the ruins of a church were still visible near the Round Tower in the middle of the eighteenth century.

Further proof of ecclesiastical occupation of the site came in the late eighteenth and early nineteenth centuries when human bones including several complete skeletons and remains of coffins were occasionally dug up in the vicinity of the Round Tower. A number of brass fastening pins, probably for monks' cloaks or shrouds, were found in conjunction with the burials, and amongst the coins discovered was one of
 Edward I.  A properly conducted archaeological excavation covering a wide area around the Round Tower would undoubtedly produce very interesting and important results.
The most obvious monastic relic is the Round Tower which stands on top of a steep eminence near the east shore of the island. It is constructed from fairly small rounded stones which may well have come from the island's shores, and is forty three feet high, but was probably somewhat higher when it was originally built. Probably in the region of seventy feet high. The original doorway was about twelve feet above ground level on the south east side of the tower, a more recent one at ground level on the west side was built up in the late 1960s to give the tower extra strength and to hinder vandals. Two fairly small windows survive further up the tower. Archaeologists have dated the Tower to the ninth or tenth century.