Trying to research the origin of the Advent wreathe will most likely produce a variety of explanations. Stories are not certain but the following explanation, adapted from an article by the Reverend William Saunders in the Arlington Catholic Herald, is a good overview of its likely development into the Christian symbol it is today.
There is evidence of pre-Christian Germanic people using wreathes with lit candles during the cold and dark days of December as a sign of hope that warmth and light would return in spring. In Scandinavia during winter, lighted candles were placed around a wheel and prayers were offered, asking the god of light to turn “the wheel of the earth” back toward the sun to lengthen the days and restore warmth.
By the Middle Ages, the Christians adapted this tradition and Advent wreathes became part of their spiritual preparation for Christmas. By 1600, both Catholics and Lutherans had more formal practices surrounding the Advent wreathe. The use of evergreens signifies continuous life – the circle, having no beginning or end, symbolizes the eternity of God. The four candles represent the four weeks of Advent. A tradition is that each one represents 1000 years, adding up to the 4000 years between Adam and Eve until the birth of the savior. The purple candles stand for the prayer, penance and sacrifices and good works that prepare us for Christmas. The rose-colored candle is lit on the third Sunday of Advent, known as Gaudete Sunday. Gaudete is Latin for “rejoice.” We rejoice because we are halfway through our preparation for the celebration of Christ’s birth. The priest also wears rose-colored vestments on that day.
The progressive lighting of the candles symbolizes the expectation and hope surrounding our Lord’s first coming into the world and the anticipation of his second coming at the end of time. The light itself stands for Christ, “…the Light that came into the world.” (cf. John 3:19-21) Some people place a white candle in the center to represent Christ. This candle is lit on Christmas day.