It is named after a woman called "Valborg" (alternative spellings are "Walpurgis", "Wealdburg", or "Valderburger") born in 710 somewhere Dorset / Wessex as a niece of Saint Boniface. Together with her brothers she later travelled to Württemberg, Germany where she became a nun and lived in the convent of Heidenheim, which was founded by her brother Wunibald. Valborg died on February 25, 779 and that day still carries her name in the Catholic calendar. However she wasn't made a saint until May 1 in the same year, and that day carries her name in the Swedish calendar. Viking fertility celebrations took place around April 30 and due to Valborg being declared a saint at that time of year, her name became associated with the celebrations. Valborg was worshipped in the same way that Vikings had celebrated spring and as they spread through out Europe the two dates became mixed together and created the Valborg celebration. This was found at: http://en.wikipedia.org/wiki/Walpurgis_Night

"Walpurgis Night (in German folklore) the night of April 30 (May Day's eve), when witches meet on the Brocken mountain and hold revels with their Gods..." "Brocken the highest of the Harz Mountains of north central Germany. It is noted for the phenomenon of the Brocken spectre and for witches' revels which reputably took place there on Walpurgis night. The Brocken Spectre is a magnified shadow of an observer, typically surrounded by rainbow-like bands, thrown onto a bank of cloud in high mountain areas when the sun is low. The phenomenon was first reported on the Brocken." —Taken from Oxford Phrase & Fable. Walpurgis is one of the main holidays during the year in both Sweden and Finland, alongside of Christmas and Midsummer. The forms of celebration in Sweden vary in different parts of the country and between different cities. One of the main traditions in Sweden is to light large bonfires, a custom which is most firmly established in Svealand, and which began in Uppland during the 18th century. An older tradition from Southern Sweden was for the younger people to collect greens and branches from the woods at twilight, which were used to adorn the houses of the village. The expected reward for this task to be paid in eggs. Today in Finland, Walpurgis Night (Vapunaatto) is, along with New Year's Eve, the biggest carnival-style festivity taking place in the streets of Finland's towns and cities. The celebration is typically centered on plentiful use of sparkling wine and other alcoholic beverages. The student traditions are also one of the main characteristics of "Vappu". From the end of the 19th century, "Fin de Siècle", and onwards, this traditional upper class feast has been co-opted by students attending university, already having received their student cap. Many people who have graduated from lukio wears the cap. One tradition is drinking mead, whose alcohol content varies. Fixtures include the capping of the Havis Amanda, a nude female statue in Helsinki, and the biannually alternating publications of ribald matter called Apy and Julkku. Both are sophomoric; but while Julkku is a standard magazine, Äpy is always a gimmick. Classic forms have included an Äpy printed on a toilet-roll and a bedsheet. Often the magazine has been stuffed inside standard industrial packages such as sardine-cans and milk cartons. The festivities also include a picnic on May 1st, which is sometimes prepared in a lavish manner. The Finnish tradition is also a shadowing of the Soviet Era May Day parade. Starting with the parties of the left, the whole of the Finnish political scene has nominated Vappu as the day to go out on stumps and agitate. This does not only include right-wing parties, but also others like the church have followed suit, marching and making speeches. In Sweden it is only the labour and socialist parties which use May 1 for political activities, while others observe the traditional festivities. Anton Szandor LaVey chose Walpurgis Night in 1966 to found the Church of Satan. Adolf Hitler, with several members of his staff (including Joseph Goebbels), committed suicide on Walpurgisnacht, April 30/May 1, 1945 http://www.answers.com/topic/walpurgis-night