The evergreen fir tree has traditionally been used to celebrate winter festivals (pagan and Christian) for thousands of years. Pagans used branches of it to decorate their homes during the winter solstice.
Saint Nicholas knew the family was very poor, so he threw three bags of gold coins down the chimney. The money landed in the sisters' stockings. Since then, children have hung up their Christmas stockings on Christmas Eve, hoping to find them filled with gifts in the morning.