The song, "The Twelve Days of Christmas" is an English Christmas carol. From 1558 until 1829, Roman Catholics in England were not permitted to practice their faith openly. Someone during that era wrote this carol as a catechism song for young Catholics.
It has two levels of meaning: the surface meaning plus a hidden meaning known only to members of the Church. Each element in the carol has a code word for a religious reality that the children could remember.
There are 12 fruits of the Holy Ghost.
The "True Love" heard in the song is not a smitten boy or girlfriend, but Jesus Christ, because truly love was born on Christmas Day.
The partridge in the pear tree also represents Him because that bird is willing to sacrifice its life if necessary to protect its young by feigning injury to draw away predators.
According to Ann Ball in her book, “Handbook of Catholic Sacramentals:”
The two turtle doves were the Old and New Testaments and the 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 represented the first five books of the Old Testament, which describe man's fall into sin and the great love of God in sending a savior.
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 – charity, joy, peace, patience (forbearance), goodness (kindness), mildness, fidelity, modesty and continency (chastity).
The 10 lords a-leaping were the Ten Commandments. The 11 pipers piping stood for the 11 faithful Apostles. The 12 drummers drumming symbolized the 12 points of belief in The Apostles' Creed.
Fr. Calvin Goodwin, FSSP, Nebraska. Catholic News Service/Catholic Tradition.