Do you know why we celebrate Halloween? Have you ever wandered why is pumpkin the iconic symbol of Halloween? Nowadays, Halloween is characterized by dressing in costumes, going trick'r'treating and watching horror films, but the history of Halloween dates around 2000 years before Christ. Halloween originates from ancient Celtic ritual of Samhain. The old Celts believed that the barriers between the physical world and the spirit world disappear in the night of Samhain, enabling the interaction between humans and those from the world of the dead. In the night of Samhain, participants of the festival including Druid priests invoked and prayed to the spirits of their ancestors for whom they believed can hear and communicate with them in the night of October 31st. Eventually, Samhain merged with Halloween. Many of the pagan traditions were swept away, after Halloween became adopted in America in 19th century through Irish and Scottish immigrants who brought trick'r'treating. Although it seems abhorrent, Christianity played a big part in spreading Halloween holiday. Some suggest that early Church may have been Christianized Samhain as All Hallow's Day, along with its eve. Other researchers believe Halloween began merely as a Christian holiday.