Her union with Lugh's father,
Cian (Cían) of the
Tuatha Dé Danann, is presented in early texts as a simple dynastic marriage, but later folklore preserves a more involved tale, similar to the birth of
Perseus in
Greek mythology. A
folktale recorded by
John O'Donovan in 1835 tells how Balor, in an attempt to avoid a druid's prophecy that he will be killed by his own grandson, imprisons Ethniu in a tower on
Tory Island away from all contact with men.
Mac Cinnfhaelaidh (Cían), whose magical cow
was stolen by Balle, gains access to Ethniu's tower, with the magical help of the
leanan sídhe Biróg, and seduces her. Ethniu gives birth to triplets, but Balor gathers them up in a sheet and sends a messenger to drown them in a whirlpool. The messenger drowns two of the babies, but unwittingly drops one in the harbour, where he is rescued by Biróg. She takes the child back to his father, who gives him to his brother,
Gavida the smith, in
fosterage. The boy grows up to kill Balor. By comparison with texts like
Cath Maige Tuired and the
Lebor Gabála Érenn, the unnamed boy is evidently Lugh, and his father, Mac Cinnfhaelaidh, is a stand-in for Cian. The
Banshenchas states that her real name was Feada: "Feada was the real name of noble Ethne who was wife of strong stout Cain, and mother of Lug the impetuous superman, and daughter of swift smiting Balor son of Dod son of mighty Net a greater man than pleasant Hector. From him is famed the cairn at Ath Feindead because he fought a duel." The
Fosterage of the Houses of the Two Methers has
St. Patrick saying of Eithne: I shall leave these virtues for the story of Eithne from the fair Maigue. Success in children, success in foster-sister or brother, to those it may find sleeping with fair women. If you tell of the fosterage before going in a ship or vessel, you will come safe and prosperous without danger from waves and billows. If you tell of the fosterage (before going to a) judgment or a hunting, your case will be (prosperous), all will be submissive before you. To tell the story of Eithne when bringing home a stately wife, good the step you have decided on, it will be a success of spouse and children. Tell the story of noble Ethne before going into a new banqueting house, (you will be) without bitter fight or folly, without the drawing of valiant, pointed weapons. Tell to a king of many followers the story of Ethne to a musical instrument, he gets no cause to repent it, provided he listen without conversation. If you tell this story to the captives of Ireland, it will be the same as if were opened their locks and their bonds. ==Popular culture==