What are the origins of Halloween?
Why do we dress up as ghosts and witches in exchange for sweets on 31 October?

Before it became the modern festival of pop-culture horror, Halloween was simply the evening before All Hallows Day – the Christian feast commemorating the dead, particularly saints and martyrs.
Introduced in the early seventh century, All Hallows Day (or All Saints’ Day) was originally a celebration of rebirth in spring. But in 835 AD , the date was switched to 1 November in an attempt to Christianise earlier pagan harvest festivals.
One such celebration was Samhain, a feast marking the start of winter. This was believed to be a time when barriers between the worlds of the living and dead were broken, and significant offerings were made to the spirits of the departed – themes echoed in ghoulish Halloween celebrations today.
Apple bobbing has been an autumn tradition for centuries and has now become a Halloween staple.