…The Roman’s celebrated their god Saturn. Their festival was called Saturnalia which began the middle of December and ended January 1st. With cries of “Jo Saturnalia!” the celebration would include masquerades in the streets, big festive meals, visiting friends, and the exchange of good-luck gifts called Strenae (lucky fruits).
…”Jo Saturnalia!” was a fun and festive time for the Romans, but the Christians though it an abomination to honor the pagan god. The early Christians wanted to keep the birthday of their Christ child a solemn and religious holiday, not one of cheer and merriment as was the pagan Saturnalia.
But as Christianity spread they were alarmed by the continuing celebration of pagan customs and Saturnalia among their converts. At first the Church forbid this kind of celebration. But it was to no avail. Eventually it was decided that the celebration would be tamed and made into a celebration fit for the Christian Son of God…
From The Story of Christmas (Christmas on the Net):