It’s December again and millions of Australians will attend a carol service or three. It remains a much-loved tradition, even in today’s secular times, but how many people will fully understand the words they are singing? Almost everybody knows that Christmas commemorates the birth of Jesus of Nazareth (c. 6 BC–c. 30 AD), the central figure of the religion now known as Christianity. Carols, it’s generally assumed, are sung for the purpose of recalling the circumstances—real or apocryphal—of that far-off event. Beyond that a lot of people are cheerfully apathetic. In fact, the lyrics of our most treasured carols go…