In the 1497 book by Caxton called “History of England, Wales, Scotland and Ireland” there is the following quotation:
It was from this legend, that Thomas Moore (1779 – 1852) found inspiration for his wonderful “Let Erin Remember the Days of Old”

Let Erin Remember the Days of Old
Let Erin remember the days of old,
Ere her faithless sons betrayed her;
When Malachi wore the collar of gold,
Which he won from her proud invader;
When her kings, with standard of green unfurled,
Led the Red-Branch Knights to danger;
Ere the emerald gem of the western world
Was set in the crown of a stranger.
On Lough Neagh’s bank as the fisherman strays,
When the clear, cold eve ’s declining,
He sees the round towers of other days,
In the waves beneath him shining!
Thus shall memory often, in dreams sublime,
Catch a glimpse of the days that are over;
Thus, sighing, look through the waves of time
For the long-faded glories they cover!
Lough Neagh & Shane’s Castle
I came across an interesting article in the People’s Advocate and Monaghan, Fermanagh, and Tyrone News, from Saturday 27th February 1897.
It is formed by the confluence of the Blackwater, the Upper Bann, and four other rivers. The only outlet is the Lower Bann emptying into the Atlantic at Coleraine, ten miles west of the Giant’s Causeway. It is about twenty miles in length, twelve in breadth, eighty in circumference, and comprises about 154 square miles.
Isle of Man Legend
The article goes on to reference a connection between Lough Neagh and the Isle of Man.
This legend is referred to by the poet Moore in his Irish melody, “Let Erin remember the days of old.
“On Lough Neagh’s banks as the fisherman strays,
When the clear, cold eve’s declining,
He sees the round towers of other days,
In the waves beneath him shining!”
It is noteworthy, too, that wherever a creek exists in the Isle of Man, a corresponding projection is found in the lake and vice-versa.
Although nearer to England than to Ireland, the language used in the Isle Man is derived from the ancient Celtic — the same as is spoken by the fishermen on the coasts of Down and Louth at the present day.
Lough Neagh is celebrated for a fish called “pollen,” in size and shape resembling the herring, but whiter when cooked. It is found nowhere else.
Jutting out on Lough Neagh is Shane’s Castle — the former residence ot the chiefs of the sept of O’Neill. The demesne of this castle stretches along the lough for over three miles, and is the oldest, largest, and best-wooded in the North of Ireland.
In 1816 the castle was accidentally burned, and a valuable library and many rare paintings destroyed. The owner of the castle, who was than making a magnificent addition to it, abandoned it after the fire, and fitted another residence.