Final answer:
Halloween originated from the ancient Celtic festival of Samhain and was later influenced by Christian practices like All Saints' Day and All Souls' Day, as well as the medieval practice of 'souling.'
Step-by-step explanation:
Halloween's origins are indeed a mix of Christian and non-Christian traditions. The holiday's roots are in the ancient Celtic festival of Samhain, a celebration marking the end of the harvest season and the beginning of winter. This period was also associated with the belief that the boundary between the living and the dead became blurred, and the deceased would come back to life and cause havoc such as sickness or damaged crops.
With the spread of Christianity, the Church instituted All Saints' Day on November 1st to honor all saints and martyrs, which was followed by All Souls' Day on November 2nd, a time to pray for the souls of the faithful departed. These days were collectively called Hallowmas. The evening before All Saints' Day became known as All Hallows' Eve, eventually evolving into Halloween. The Christian church tried to reinterpret the pagan festivals with a Christian meaning, as a strategy to convert pagans to Christianity.
Today's Halloween customs also derive from these ancient traditions mixed with Christian practices. For example, wearing costumes and lighting candles can be traced back to the Celtic traditions of warding off evil spirits, whereas the practice of trick-or-treating evolved from the medieval Christian practice of 'souling,' when the poor would go door to door on Hallowmas receiving food in exchange for prayers for the dead.