In the roman year December was the tenth month derived from the word 'decem' meaning ten.
The Anglo Saxons called it the winter month, or yule month, due to the custom of burning the yule log. It marked the beginning of winter when the weather changed.
Many of our Christmas customs began long before Jesus was born. They came from earlier festivals which had nothing to do with the Christian church. Celebrated in the mid-winter when the days were shorter and the sunlight weakest. They believed the festivals would give the sun back it's power.
Romans had the festival of Saturnaua on about December 25th. They decorated their homes with evergreens to remind them of Saturn, their harvest god. Some of these customs were continued by the early Christians.
The December solstice is the winter solstice in the northern hemisphere and the summer solstice in the southern hemisphere. The day has astronomical, cultural and religious significance. The longest night being December 21st, and therefore the shortest day. A great excuse to have a party held in the afternoon because of the short daylight hours.
Advent was the beginning and preparation for the feast of Christmas. December, the Christmas month, commemorating the birth of Jesus. Nowadays people from all over the world celebrate the birth of Jesus on the 25th December.
However Christmas cards and crackers came from the Victorian era, and Father Christmas is believed to be from the story of St Nicholas. You can read more about him here.