This article accompanies the fable
That wasn't all Robert Rochfort was jealous about.
After the death of his first wife from smallpox, Robert had married his second wife Mary Molesworth in 1736 and they had four children. Some time around 1742 he suspected Mary of adultery with his other brother Arthur. Robert sued Arthur, who ended up in debtor's prison (he died there), and Robert locked Mary away (with servants) in the family home at Gaulstown House for more than 30 years, while he went and lived nearby at his new mansion at Belvedere. Her loneliness eventually drove her mad. Full story here.
The Jealous Wall came later. Below is what he was jealous about when he built the Wall: Tudenham Park, which is now a real ruin without a roof (since 1957), but protected by Ireland's Department of the Environment, Heritage and Local Government.
Before all this transpired, up through the 1720's, a close family friend and regular visitor to the Rochfort family home at Gaulstown, was Jonathan Swift. Several of his most famous letters - such as A Letter to a Young Lady, on her Marriage (1727) - are addressed to Rochfort family members and it is said that Lilliput in Gulliver's Travels (written 1721-25) was inspired by his time spent there and on the nearby Lough Ennell. After its publication in 1726, the SW part of the lake was renamed Lilliput in honor of the book - Lilliput House (shown below) dates from the 18th century.