A banshee ( BAN-shee; Modern Irish bean sí, from Old Irish: ben síde [b?en '?i:ð?e], "woman of the fairy mound" or "fairy woman") is a female spirit in Irish folklore who heralds the death of a family member, usually by wailing, shrieking, or keening. Her name is connected to the mythologically important tumuli or "mounds" that dot the Irish countryside, which are known as síde (singular síd) in Old Irish.
Sometimes she has long streaming hair and wears a gray cloak over a green dress, and her eyes are red from continual weeping. She may be dressed in white with red hair and a ghastly complexion, according to a firsthand account by Ann, Lady Fanshawe in her Memoirs. Lady Wilde in Ancient Legends of Ireland provides another:
The size of the banshee is another physical feature that differs between regional accounts. Though some accounts of her standing unnaturally tall are recorded, the majority of tales that describe her height state the banshee's stature as short, anywhere between one foot and four feet. Her exceptional shortness often goes alongside the description of her as an old woman, though it may also be intended to emphasize her state as a fairy creature.
In O'Brien's Irish- English Dictionary the entry for Síth-Bhróg states:
"hence bean-síghe, plural mná-síghe, she-fairies or women-fairies, credulously supposed by the common people to be so affected to certain families that they are hears to sing mournful lamentations about their houses by night, whenever any of the family labours under a sickness which is to end by death, but no families which are not of an ancient & noble Stock, are believed to be honoured with this fairy privilege".
Sometimes the banshee assumes the form of some sweet singing virgin of the family who died young, and has been given the mission by the invisible powers to become the harbinger of coming doom to her mortal kindred. Or she may be seen at night as a shrouded woman, crouched beneath the trees, lamenting with veiled face, or flying past in the moonlight, crying bitterly. The cry of this spirit is mournful beyond all other sounds on earth, and betokens certain death to some member of the family whenever it is heard in the silence of the night.
In Ireland and parts of Scotland, a traditional part of mourning is the keening woman (bean chaointe), who wails a lament--in Irish: Caoineadh, pronounced ['ki:n?i:] (Munster dialect), ['ki:n] (Connaught dialect) or ['ki:n?u:] (Ulster dialect), caoin meaning "to weep, to wail". This keening woman may in some cases be a professional, and the best keeners would be in high demand.
Irish legend speaks of a lament being sung by a fairy woman, or banshee. She would sing it when a family member died or was about to die, even if the person had died far away and news of their death had not yet come. In those cases, her wailing would be the first warning the household had of the death.
The banshee also is a predictor of death. If someone is about to enter a situation where it is unlikely they will come out alive she will warn people by screaming or wailing, giving rise to a banshee also being known as a wailing woman.
It is often stated that the banshee laments only the descendants of the pure Milesian stock of Ireland, sometimes clarified as surnames prefixed with O' and Mac, and some accounts even state that each family has its own banshee. One account, however, also included the Geraldines, as they had apparently become "more Irish than the Irish themselves," countering the lore ascribing banshees exclusively to those of Milesian stock. Another exception was the Rossmore banshee which supposedly heralded the death of a member of the family of Baron Rossmore, whose ancestry was predominantly Scottish and Dutch.
When several banshees appear at once, it indicates the death of someone great or holy. The tales sometimes recounted that the woman, though called a fairy, was a ghost, often of a specific murdered woman, or a mother who died in childbirth.
Most, though not all, surnames associated with banshees have the Ó or Mc/Mac prefix - that is, surnames of Goidelic origin, indicating a family native to the Insular Celtic lands rather than those of the Norse, English, or Norman. Accounts reach as far back as 1380 to the publication of the Cathreim Thoirdhealbhaigh (Triumphs of Torlough) by Sean mac Craith. Mentions of banshees can also be found in Norman literature of that time.
The Ua Briain banshee is thought to be named Aibell and the ruler of 25 other banshees who would always be at her attendance. It is possible that this particular story is the source of the idea that the wailing of numerous banshees signifies the death of a great person.
In some parts of Leinster, she is referred to as the bean chaointe (keening woman) whose wail can be so piercing that it shatters glass. In Scottish folklore, a similar creature is known as the bean nighe or ban nigheachain (little washerwoman) or nigheag na h-àth (little washer at the ford) and is seen washing the bloodstained clothes or armour of those who are about to die. In Welsh folklore, a similar creature is known as the cyhyraeth.
Banshees, or creatures based upon them, have appeared in many forms in popular culture.
[Its occurrence] is most strongly associated with the old family or ancestral home and land, even when a family member dies abroad. The cry, linked predominantly to impending death, is said to be experienced by family members, and especially by the local community, rather than the dying person. Death is considered inevitable once the cry is acknowledged.
Most manifestations of the banshee are said to occur in Ireland, usually near the home of the dying person... but some accounts refer to the announcement in Ireland of the deaths of Irish people overseas... It is those concerned with a death, at family and community levels, who usually hear the banshee, rather than the dying person.
sir walter scott letters on demonology banshee.