I did know this but just found it somewhere online.
It's interesting so I wanted to share it...
The 12 Days of Christmas" is in a sense an allegory. Each of the items in the song represents something significant to the teachings of the Catholic faith. The hidden meaning of each gift was designed to help Catholic children learn their faith. The song goes, "On the first day of Christmas my true love gave to me…" The "true love" mentioned in the song refers to God Himself. The "me" who receives the presents refers to every baptized person. i.e. the Church.
1st Day: The partridge in a pear tree is Christ Jesus upon the Cross.
2nd Day: The "two turtle doves" refers to the Old and New Testaments.
3rd Day: The "three French hens" stand for faith, hope and love.
4th Day: The "four calling birds" refers to the four evangelists who wrote the Gospels-Matthew, Mark, Luke and John.
5th Day: The "five golden rings" represents the first five books of the Bible, also called the Jewish Torah: Genesis, Exodus, Leviticus, Numbers and Deuteronomy.
6th Day: The "six geese a-laying" is the six days of creation.
7th Day: The "seven swans a-swimming" refers to the seven gifts of the Holy Spirit: wisdom, understanding, counsel, fortitude, knowledge, piety and fear of the Lord.
8th Day: The "eight maids a milking " reminded children of the eight beatitudes listed in the Sermon on the Mount.
9th Day: The "nine ladies dancing" were the nine fruits of the Holy Spirit found in Galatians: love, joy, peace, patience, kindness, goodness, faithfulness, gentleness and self control.
10th Day: The "ten lords a-leaping" represents the Ten Commandments.
11th Day: The "eleven pipers piping" refers to the eleven faithful apostles.
12th Day: The 'twelve drummers drumming" were the twelve points of belief expressed in the Apostles' Creed: belief in God the Father, the Son and the Holy Spirit, that Jesus Christ was born of the Virgin Mary, made man, crucified, died and arose on the third day, that he sits at the right hand of the father and will come again, the resurrection of the dead and life everlasting.