The partridge in a pear tree was Jesus Christ.
Two turtle doves were the Old and New Testaments.
Three French hens stood for faith, hope and love.
The four calling birds were the four gospels of Matthew, Mark, Luke, and John.
The five golden rings recalled the Torah or Law, the first five books of the Old Testament.
The six geese a-laying stood for the six days of creation.
Seven swans a-swimming represented the sevenfold gifts of the Holy Spirit -- Prophesy, Serving, Teaching, Exhortation, Contribution, Leadership, and Mercy.
The eight maids a-milking were the eight beatitudes.
Nine ladies dancing were the nine fruits of the Holy Spirit -- Love, Joy, Peace, Patience, Kindness, Goodness, Faithfulness, Gentleness, and Self Control.
The ten lords a-leaping were the ten commandments.
The eleven pipers piping stood for the eleven faithful disciples.
The twelve drummers drumming symbolized the twelve points of belief in the Apostles' Creed.
Merry (Twelve Days of) Christmas!