Today (December 25) is the first day of Christmas...when "My True Love Gave To Me...A Partridge In A Pear Tree." WHAT? Pear trees do not have anything to do with Christmas...at least not from my town. And then the other verses: Turtle doves, Lords A Leaping, French Hens, Swans Swimming, etc. (I have some great jokes about the French.)
There are those who believe the song originated in England when Catholics were prohibited from practicing their religion, openly or privately, between 1558 and 1829 by Protestant Monarchs. According to this belief the song used the verses as hidden meanings to teach Catholic dogma to the children. Snoops illustrates this to be false, or at least highly unlikely. Others suggest no secret religious meaning, but do suggest the song verses have a deeper meaning. Meridian Magazine and Appleseeds both suggest the same meaning for each verse. (By the way, both Meridian and Appleseeds refer to the teaching of young the dogma of the Christian church which Snoops decries. As Snoops observed: How can you believe that it is a song to put Christ into Christmas when is it purported to reflect the fact that one group of Christians had to hide in order that another group of Christians would not torture and kill them for their beliefs?) If you Google the 12 Days of Christmas you will find numerous other sites with the same general ideas contained in Meridian and Appleseeds. So, false or not, it appears to be here to stay.
No one really knows the true origin or intent of the song. There are speculations. Wikipedia provides both. Whatever the religious meaning, I prefer the version of the song by Bob and Doug Mckenzie in their Great White album. Here is a YouTube version.