Ancient Romans celebrated Saturnalia, a week long tradition of holiday parties from December 17-23, which encompassed the time of the Winter Solstice. People were celebrating their abundant harvests and successes and bringing light and joy into their homes and their towns and giving thanks to their god Saturn. There was much frivolity, drinking and sexual play, mischief, music, dance and feasting. Today, many of the old pagan customs have survived as folk lore.
Ancient Germanic people give us the word Yule, which was a
12 day celebration held at this same period of time. It was from these people that we got the traditions of the wassail, yule log, bringing evergreens inside the house, wreaths, garlands and trees, as well as the roast boar, which is why some people prefer ham as a holiday meal. The toast Wassail! means "to your health" and was usually made with a hot cider, often spiked with alcohol, of course.
It was in the 4th century that the new religion of Christianity had tried unsuccessfully to get the people to give up their old pagan traditions, so they moved the feast of Christ's birth to the same date as these old pagan holidays. So they simply declared all celebrations at this time of year to be celebrations of Christ's birth. The church used the psychological ploy of "if you can't lick 'em, join 'em."