Listen to this description of the influence of paganism in the practice of the early church, offered by Joseph Duggan. He says,
One of the most prominent and popular of the pagan ceremonies was the Saturnalia running from the 17th to the 24th of December, followed by the Brumalia on the next day. It was a time of great celebration, merry-making and the giving of gifts. All this was to celebrate the victory of the unconquerable sun-god over darkness at the winter solstice, when the sun is at its lowest point and the days begin to lengthen. It was one thing for the church, now popular and dominant in Rome, to persuade the people to give an outward profession of her religion. But to persuade them to surrender age-old practices was another matter. The most expedient thing to do was to let the people keep their old pagan festivals while recasting them in an outwardly Christian form. (bold mine)
And so the imagery of Saturnalia was changed from the worship of the sun-god to the worship of the Son of God. The similarities were accentuated. The sun-god had been likened to a small child… perfect. The sun-god has been regarded as unconquerable… Gift giving was retained, but the gifts were now given in the name of Christ. All of this seemed harmless enough to the Roman Church. In fact, they were operating under what could be conceived of as a commendable motive: bringing the un-saved into the church. But the end does not justify the means, especially if the means are clearly condemned by the Word of God. In the end, principle had been compromised for the sake of expediency, and this is always a dangerous course.