The tradition of placing a candle in a pumpkin seems to have several origins. Believe it or not, in Medieval times people used the skull of a dead family member as a candle holder which was placed outside the front door as a means of keeping spirits at bay.
In the United States, carved pumpkins are known as Jack O 'Lanterns due to an old Irish folk tale. There once lived a villain called Jack who, having struck a deal with the Devil to never take his soul, was condemned to wander aimlessly after he died, as he was not fit to enter heaven either. With only a hot ember to light his way, Jack placed it inside a gouged out vegetable to act as a lantern.
Jack O' Lanterns were originally carved out of turnips, but Irish emigrants to America adopted the plentiful pumpkin because it’s much easier to carve.
Nowadays, bonfires are more closely associated with Guy Fawkes night, but originally they were very much part of the Halloween celebrations. The fires were usually built on the top of a hill and surrounded by a circular trench to represent the sun. It was believed the fires kept evil spirits away and would also encourage the sun to return at the end of winter.
A flaming brand was then taken from the fire and used to light fires in the homes of all the villagers to protect them through the coming months. There are different rituals throughout most Celtic countries that relate to the fire: in Scotland, newly-engaged couples threw nuts into the flames. If the nuts burnt silently, the marriage would be happy, but if they spat or hissed, it suggested trouble ahead.