(in Irish folklore) a spirit in the form of a wailing woman who appears to or is heard by members of a family as a sign that one of them is about to die.
Origin of banshee
1765–75; < Irish bean sīdhe woman of a fairy mound; see sídh
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019
(in Irish folklore) a female spirit whose wailing warns of impending death
Word Origin for banshee
C18: from Irish Gaelic bean sídhe, literally: woman of the fairy mound
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012
1771, from phonetic spelling of Irish bean sidhe "female of the Elves," from bean "woman" (from PIE *gwen-; see queen) + sidhe, from sith "fairy" or sid "fairy mound." Specifically, one who calls to the spirits of the dead.
Online Etymology Dictionary, © 2010 Douglas Harper