There's some great stuff on this thread, and I love it to bits but I don't think any of these titles will help much in answering Joe's original question about 12 Days of Christmas. I couldn't find an answer to that one either, but some related stuff on seasonal/ritual songs is in A. L. Lloyd's Folksong in England (mentioned above) and R. J. Stewart's Pagan Imagery in English Folk Song. This book is also called Where is Saint George: pagan imagery in English folk song Sometimes this author publishes under "Bob", sometimes "Robert J.", sometimes "R. J." The book is out of print under either title, of course. All the neat books I really want are out of print. Long live interlibrary loan and the photocopier!