The Origins of Halloween

As far as I know one of the versions, the authorship of the holiday is attributed to the druids — the Celtic people who lived in Ireland. The progenitor of Halloween was the Samhain holiday, which was celebrated at the end of October. Samhain meant the end of summer.On this day, they thanked for the harvest, burned sacred bonfires, seeing off the old year and welcoming the new one.
The Celts believed that on Halloween the spirits of the dead walk among the living. In order for the spirits of the ancestors to contribute to a good harvest next year, they tried to appease them with treats and gifts. It was this custom that transformed into trick-or-treating, "muck or sweetness" - a children's Halloween tradition of going home begging for candy.
Some believe that Halloween is in some way a Christian holiday, because it is celebrated on the eve of All Saints' Day.

Witches
The witch's outfit, as for me, is the most popular female costume for Halloween, and the silhouette of a witch on a broom against the background of a full moon is one of the typical symbols of the holiday. It is believed that on the night of the first of November, the power of witches increases many times. The image of an old witch in a pointed hat stirring her brew in a huge cauldron was transformed from the pagan image of the goddess known as Mother Earth or the Old Woman, and symbolizing wisdom and the change of seasons.