Dalkey Island and it's Church 

Dalkey island is a small island less than one kilometre from the mainland. It contains just over ten hectares or 21 acres, largely rough grazing, scrub and rock. The name is Norse, a direct translation from the Irish, Deilginis, meaning thorn island. It is clearly a topographical name, reflecting the shape of the island and its attendant islets and rocks. It names also the town on the mainland but there is some indication that it applied only to the island originally and that the mainland settlement was known as Cellbegnat.
There has been human activity on the island for thousands of years. There was a small promontory fort there in the early middle ages which may have been a trading centre; excavation revealed late-Roman and post-Roman pottery among other finds. The earliest historical reference to the island is in the tenth century. The Annals of the Four Masters record under the year 938 ‘Coibhdeanach, abbot of Cill-achaidh, was drowned in the sea of Deilginis-Cualann while fleeing from the foreigners’. The Vikings held captives there before they were sold into slavery.
The small stone church on the island is, according to Chris Corlett ‘a classic example of an eleventh century Irish church’ (a belfry was added in the late Middle Ages). It was presumably a hermitage chapel, similar to those on St. Patrick’s Isle off Skerries and on Ireland’s Eye off Howth. It was dedicated to the local patron, St. Begnet, who is said to have lived there as a hermit. Its function is not clear; the island was largely uninhabited except perhaps in the summer when cattle or sheep may have been grazed there. The grazing was said to be worth 12d in 1326. At an inquisition taken 1257-63 it was said that a man who stole an anchor at Dalkey fled to the chapel on the island (in other words claimed sanctuary). He later swore to leave the area.  The chapel gradually went out of use after the parish church was built on the mainland. There is a well near the chapel dedicated to St. Begnet but there is no evidence that it nor the chapel were ever centres of pilgrimage. In fact, the well’s dedication seems to have been lost;  its popular name was the scurvy well as the waters were regarded as a cure for scurvy.