From 1558 to 1829 the Catholics in England were not able to practice their faith openly so they had to find other ways to pass on their beliefs. Each of the items in the song represents something of religious significance. The hidden meaning of each gift was designed to help young Christians learn their faith.
A Partridge in a Pear Tree
The "partridge in a pear tree" is Jesus Christ who died on a tree or cross as a gift from God for the whole world.
Two Turtle Doves
Two turtle doves are symbolic of theĀ Old and the New Testament
Three French Hens
The three French hens are symbolic of the valuable poultry during that time, only for the rich could afford, like the wise men's gifts of gold, frankincense, and myrrh.
Four Calling Birds
The four calling birds are symbolic of the four Gospel writers, like birds calling out with loud and distinctive voices.
Five Golden Rings
The 5 golden rings are symbolic of the the Torah (the 5 books of Moses), treated as most valuable and treasured, as is gold.
Six Geese A-laying
The six geese are symbolic of the six days of new life, the creation.
Seven Swans A-swimming
The swans are symbolic of the the seven gifts of the Holy Spirit that also change us from ugly ducklings into graceful adults.
Eight Maids A-milking
The eight maids milking are symbolic of the beatitudes
Nine Ladies Dancing
The nine ladies dancing are symbolic of the rejoicing over the nine fruits of the spirit. (love, joy, peace, patience, kindness, goodness, faithfulness, gentleness, and self control)
Ten Lords A-leaping
The ten lords leaping are symbolic of the ten commandments.
Eleven Pipers Piping
The eleven pipers piping are symbolic of the piping the eleven faithful apostles following the chief piper and becoming like Him.
Twelve Drummers Drumming
The twelve drummers drumming are symbolic of the loud steady rhythm for marchers to follow as is the points of the Apostle's Creed