In legend, a Banshee wails nearby if someone is about to die. There are some special families who are believed to have Banshees attached to them, and whose cries herald the death of a member of that family. Most, though not all, surnames associated with Banshees have the Ó or Mac prefix. They were also associated with the Airlie clan. Accounts of Banshees go back as far as 1380 with 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 Ban Si was also known to wail at the crowning of the true king. Such a cry was reported to be heard at the crowning of Brian Boru.
Traditionally, when a person died a woman would sing a lament (in Irish: caoineadh, [ˈkɰiːnʲə] or [ˈkiːnʲuː], "caoin" meaning "to weep, to wail") at the funeral. These women are sometimes referred to as "keeners" and the best keeners would be in much demand. Legend has it that for five great Gaelic families — the O'Gradys, the O'Neills, the Ó Briains, the Ó Conchobhairs, and the Caomhánachs — the lament would be sung by a fairy woman; having foresight, she would sing it when a family member died, even if the person had died far away and news of their death had not yet come, so that the wailing of the Banshee was the first warning the household had of the death.
The Ó Briains' Banshee was thought to have the name of Eevul, and was ruler of 25 other Banshees who would always be at her attendance. It is thought that from this myth comes the idea that the wailing of numerous Banshees signifies the death of a great person.
In later versions, the Banshee might appear before the death and warn the family by wailing. When several Banshees appeared at once, it indicated 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.
Banshees are frequently described as dressed in white or grey, often having long, pale hair which they brush with a silver comb, a detail scholar Patricia Lysaght attributes to confusion with local mermaid myths. This comb detail is also related to the centuries-old traditional romantic Irish story that, if you ever see a comb lying on the ground in Ireland, you must never pick it up, or the Banshees (or mermaids — stories vary), having placed it there to lure unsuspecting humans, will spirit such gullible humans away. Other stories portray Banshees as dressed in green, red, or black with a grey cloak. look at this a couple hints we have seen