When it was a crime to be Catholic and to practice one's faith in Ireland and England "The Twelve Days of Christmas" was written as a "catechism song" to help the young learn their faith. It was a memory aid-when being caught with anything in writing about the faith could get you imprisoned, even hung. The gifts hide the teachings of the faith. The "true love" mentioned in the song refers to God himself. The "me" who receives the presents refers to every baptized person.
A Partridge in a pear tree = Jesus Christ, the son of God.
Two turtle doves = The Old and New Testaments
Three french hens = Faith, Hope and Charity, the theological virtues.
Four calling birds = The four Gospels and/or the four Evangelists.
Five golden rings = The first five books of the Old Testament
Six geese a-laying = Six days of creation.
Seven swans a swimming = The seven Sacraments.
Eight maids a-milking = The eight Beatitudes.
Nine ladies dancing = The nine classifications of angels).
Ten lords a-leaping = The Ten Commandments.
Eleven pipers piping = The eleven faithful apostles.
Twelve drummers drumming = The twelve points of doctrine in the Apostle's Creed.