Halloween can trace its lineage to Samhain (pronounced Sowen) practiced by the ancient Celtic cultures of the British Isles. Today's modern Wiccans or witches celebrate Samhain as one of their high holidays, harkening back to many of the age-old Druidic practices. Translated as "summer's end," Samhain isconsidered an ideal time for magic and communing with the spirits, as the veil between our world and the next is said to be at it's thinnest. For more, see articles on Witchvox(1) and Wicca.com(2).

1. http://www.witchvox.com/va/dt_va.html?a=usma&c=holidays&id=2204
2. http://www.wicca.com/celtic/akasha/samhainlore.htm