Another possibility is that the Girt Dog burning his tail has to do with the heliacal rising of the "tail" star of the Great Dog (Canus Major) - that is the night "we are going wassail".

I'm perplexed by the maid with the silver-headed pin - which sounds like another stellar reference - for Casseopea and Virgo are both far away from Canus Major. Anyone have an idea of which constellation the maid was/is?