Walpurgis Night (), an abbreviation of Saint Walpurgis Night (from the German Sankt-Walpurgisnacht [zaŋkt valˈpʊʁɡɪsˌnaxt]), also known as Saint Walpurga's Eve (alternatively spelled Saint Walburga's Eve) and Walpurgisnacht, is the eve of the Christian feast day of Saint Walpurga, an 8th-century abbess in Francia, and is celebrated on the night of 30 April and the day of 1 May. This feast commemorates the canonization of Saint Walpurga and the movement of her relics to Eichstätt, both of which occurred on 1 May 870.
https://en.wikipedia.org/wiki/Walpurgis_Night