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 their church.
Each element of the carol has a code word for a religious reality, which the children could remember.
1. The "partridge in a pear tree" was Jesus Christ.
2. "Two turtledoves" were the Old and New Testaments.
3. "Three French hens" stood for faith, hope and love.
4. The "four calling birds" were the four gospels of Matthew, Mark, Luke and John.
5. The "five golden rings" recalled the Torah or Law, the first five books of the Old Testament.
6. The "six geese a-laying" stood for the six days of creation.
7. "Seven swans a-swimming" represented the sevenfold gifts of the Holy Spirit:
Prophesy, Serving, Teaching, Exhortation, Contribution, Leadership, and Mercy.
8. The "eight maids a-milking" were the eight beatitudes.
9. "Nine ladies dancing" were the nine fruits of the Holy Spirit --
Love, Joy, Peace, Patience, Kindness, Goodness Faithfulness, Gentleness and Self-Control.
10. The "ten lords a-leaping" were the Ten Commandments.
11. The "eleven pipers piping" stood for the 11 faithful disciples.
12. The "twelve drummers drumming" symbolized the 12 points of belief in the Apostles' Creed.
There you have it...the hidden meaning of the Twelve Days Of Christmas and the secret behind the song.