The 12 Days Of Christmas: A secret code for persecuted Catholics?

Four calling birds, three French hens, two turtle doves and a partridge in a pear tree are familiar items in the much-loved carol the 12 Days Of Christmas.

To many who have heard dozens of adaptations, the song seems to bring together a random bunch of animals and people like "eight maids a-milking" and "11 pipers piping".

But the meaning behind the familiar and cheerful song may have been closely tied with religious teachings, according to historical theologian Associate Professor Bronwen Neil from the Australian Catholic University.

The 12 Days Of Christmas — usually interpreted to be a countdown to Christmas day by marketers — may have been in fact a secret teaching tool for Catholics during the 18th and 19th century.

While the original songwriter is unknown, the English version first appeared in a children's book in 1780.

Dr Neil said that in 1979, Canadian hymnologist Hugh McKellar floated the idea that the song had a secret code  a theory she said "had merit" but could not be proven.

"The carol was a secret catechism for Catholics in England when Catholicism was persecuted during the war of religions from Henry the VIII to 1829," Dr Neil told 702 ABC Sydney.

"This song gave them a chance to teach their kids knowledge of the saints and doctrine in a secret code when the Protestants were cracking down on the Catholics."

The true 12 days of Christmas varies across some 50 religious denominations, but the Catholic version has the Christmas season starting on December 25 and concluding with the Epiphany.

Each day represents the celebration of a martyr, saint or a feast connected with Jesus' birth.

Boxing Day for example, considered day two of Christmas, is the Feast of Saint Stephen, a deacon who gave present boxes to the poor.

"The feast wraps up on January 6, which is the revelation of Christ as the saviour and son of God to the world," Dr Neil explained.

"On that day, the Orthodox celebrate the baptism of Christ and the Catholics celebrate the arrival of the Magi — the three wise men with their presents [and] it's in their memory that we give presents."

The secret code

According to Ms Neil, each item in the 12 Days Of Christmas song was a metaphor for a bible story.

"On the first day of Christmas my true love gave to me, a partridge in a pear tree," symbolising God (true love) and Jesus Christ (the partridge).

Second day: Two turtle doves were the Old and New Testaments.

Third day: Three French hens represented the three gifts of faith, hope and love.

Fourth day: Calling birds were the four gospels.

Fifth day: Five golden rings were the Books of Moses.

Sixth day: Geese a-laying stands for the six days of creation.

Seventh day: Swans a-swimming were the seven gifts of the Holy Spirit.

Eighth day: Maids a-milking were the eight beatitudes.

Ninth day: Ladies dancing were the nine fruits of the Holy Spirit such as charity, peace and kindness.

Tenth day: Lords a-leaping represent the 10 Commandments.

Eleventh day: Pipers piping were the 11 apostles.

Twelfth day: Twelve drummers drumming represented the points of the Apostles Creed.