1. Most often implied by variants Eithlenn and Ethniu. Usually described as a daughter of Balor, king of the Fomorians, and mother of Lug Lámfhota; sometimes also described as the mother of the Dagda and Ogma. According to the Lebor Gabála [Book of Invasions], she was mated with Cian, usually a son of Dian Cécht, to promote an alliance between her people and the Tuatha Dé Danann; in later tradition she is described as a virgin, and Lug's conception implies no political agenda. When a druid tells Balor that his daughter will bear a grandson destined to slay him, he confines Eithne to a high tower on Tory Island, guarded by twelve women to keep her away from men. The plan might have worked if Balor had not desired to own Glas Ghaibhleann, a magical cow that gave endless supplies of milk. In what appears to be the oldest version of the story, Balor steals the cow from Cian, who seeks revenge, with the help of Biróg, a female druid, by dressing himself as a woman, entering Eithne's tower on Tory Island, and impregnating her, producing three children, one of whom was Lug. In a version better known in oral tradition Glas Ghaibhleann belongs to Gaibhlín, a smith, who lives with his two brothers, Mac Samthainn and Mac Cennfaelaidh, the latter a lord of the district. When the cow is stolen Mac Cennfaelaidh seeks revenge with the help of a druid and a fairy, gaining access to Eithne and impregnating her. Again Eithne gives birth to three children, but Balor attempts to kill all three by having them carried off in a blanket; two fall out but Lug survives. In a variant of this version Mac Cennfaelaidh also impregnates all twelve of the guardians, whose children become seals. In neither version does Lug thrive until taken back to Tory Island. In still another variant Eithne is the daughter of Delbáeth (1).
In the Fenian Cycle, Eithne (1) was thought to have married Nuadu Airgetlám, founding the family line that eventually produced Fionn mac Cumhaill.
2. Wife of Elcmar, an early ruler of Brug na Bóinne, in an alternative version of Angus Óg's birth. Seduced through a trick by Eochaid Ollathair (the Dagda), she conceived the divine son, Angus. Her name here may be a variant of Boand (the Boyne River).
3. Chief character of Altrom Tige Dá Medar [The Nurture of the Houses of the Two Milk Vessels]. A child of the wife of the steward of Angus Óg, she refused the food of the Tuatha Dé Danann and died embracing Christianity.
4. Sometimes known as Eithne (or Ethna) the Bride, the beautiful young woman who spends a year in the realm of the fairies with Finnbheara (or Finvara), the king of the Connacht fairies, in a story known from oral tradition. Eithne is such a beautiful young bride that her proud husband holds many festivities in her honour. One evening as she is dancing, she falls in a swoon. Nothing will revive her, and she sleeps deeply through the night. In the morning she seems to revive but will speak only of a beautiful country she has visited and to which she longs to return. The next night her old nurse is set to guard her, but she too falls into deep sleep, and in the morning Eithne is gone. When she cannot be found it is clear the fairies have some role in her disappearance, and so her husband rides to Finnbheara's mound at Cnoc Mheadha [Knockmagha, etc.], Co. Galway, to seek advice. Although the husband's castle is near Finnbheara's abode, the mortal does not fear the fairy king, leaving him offerings of wine and thinking him a friend. But when the husband approaches Finnbheara's rath, he overhears voices talking about his missing bride: that Finnbheara is happy now because he has her, and that her husband will never see her again unless he can succeed at the daunting task of digging a hole deep enough to let light into Finnbheara's underground dwelling.
The husband gathers workers from far and wide, but their work is discouraging. Every night when they cease digging the hole fills up and grows over with grass as if they have done nothing. On successive days he increases the number of workers, but to no avail. Then he hears a voice in the air advising that he sprinkle the earth with salt, which he does. He finds Eithne as beautiful as ever, but when he carries her back to the palace she will not speak or move, causing the household to fear she has eaten fairy food. Again the husband takes advice from friendly voices in the air. He removes the fairy girdle from around her waist and burns it, and puts the fairy pin holding it under a fairy thornbush, where no one will disturb it. She then sits up and stretches out her arms to him. Although she remembers everything that has happened, her year in fairyland seems but one night.
Eithne (4) bears some relationship with Eithne (3), who, in Altrom Tiga Dá Medar [The Nurture of the Houses of the Two Milk Vessels], is insulted by Finnbarr, a member of the Tuatha Dé Danann. In addition many commentators have seen a link between Eithne (4) and Eurydice of Greek tradition, rescued from Hades by Orpheus. In medieval versions of the story, known as Sir Orfeo or King Orfeo in English, Pluto [Hades] is known as the ‘king of the fairies’. Folk motifs: F322, F322.2, F375. See Lady Jane Wilde, Ancient Legends, Mystic Charms and Superstitions of Ireland (2 vols., London, 1887).
5. Early wife of Conchobar, daughter of Eochaid Feidlech, and sister of Clothra, Medb, and Mugain
6. Wife of King Rónán of Leinster and mother of Máel Fothartaig in Fingal Rónáin [How Rónán Slew His Son].
