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by Deborah Shelton Wood


The Costellos of Ireland were once MacCostello. They had possession of a large part of Sliabh Lugha region. In 1257 they built a castle on the site of the ancient Aileac Mor (or Castlemore), a property they which they owned until 1587. They were then disposessed and moved to various parts of Ireland.

The family of one Thomas Costello, known as Thomas of Laidir, settled in Tallaghan. He had a son also named Thomas or Tomas. Tomas was known for this courage and honesty.

Near Tallaghan, there lived the Chieftan of Moylurg, a Celtic Kingdom in North Roscommon. He was known as MacDermott. He had a beautiful daughter with long, flowing, blonde hair. He named her Una Bahn.

Una Bhan MacDermottand Tomas Costello of Laidir fell in love and wished to marry but MacDermott would not allow the marriage. He believed Tomas Costello of Laidir was not good enough for his daughter. Tomas was banished from the area and MacDermott had his beautiful daughter,Una Bhan,confined on Castle Island, Lough Key, then called "The Rock", which was located in the center of MacDermott territory.

Una Bhan went into a deep melancholy. Everyone said she was dying of grief. Tomas Costello of Laidir, hearing of the situation went to see her. He begged her to go with him. She promised to ask her father. When he left, he vowed that if MacDermott did not send a message for him to return before he reached the river, he would never go back. The MacDermott messenger was sent, but did not reach Tomas of Laidir until after he had crossed the river. Being a man of great honour, Tomas Costello of Laidir was unable to break his vow and did not return.

Una Bhan died of a broken heart and was buried on Trinity Island. In his grief, Tomas Laidir would often swim to the island at night to sit at her grave. Tomas contracted pneumonia. Realizing that he was dying, requested that MacDermott allow him to be buried beside his one true love, Una Bhan. His request was granted and thus the two lovers were belatedly united in the afterlife.

Tradition says that two trees grew up over the graves of Tomas Costello and Una Bhan MacDermott. The two trees are entwined together, forming a Lovers Knot, and standing guard over the graves of the two Irish star-crossed lovers.

by Deborah Wood

Trinity Island where the lovers are buried.

The love story has survived all this time. It has been the subject of several songs. Here is part of one of the oldest Irish ballads:

The Legend of Una Bhan

"On Trinity the green leaves blow,

high where Una Bhan and Tomas Ladir lovers tie.

Each day the lark sings from the blue,

sky above bitter sweet song,

of their romantic love".

Copyright 1998, 2006 Deborah Shelton Wood - All Rights Reserved

Back to the Costello page

Back to the Behr Family History page

Sources: My information regarding this legend came from these great websources:

Irish Country Holidays

Una Bahn, Rural Tourism Site:

The New Oxford Book of Irish Verse