This song arose from my understanding of Brighid as a hearth goddess, and three of her more famous symbols and aspects (the harp of inspiration, the cup of healing, and the hammer of the forge) come out of that role as the creator and protector of homes. Throughout the Indo-European range, a fire was what made a building a home at least as much as having, say, a bed, which makes sense as something humans have been using for warmth and protection since before we were modern humans.
Musically, this is pretty straight-forward waltz time (honoring Brighid's favorite number of 3 with 3 beats to the measure). However, one slightly unusual aspect of it is the G mixolydian scale, which is similar to G major, but has the F natural instead of the F sharp, which helps to move the song into the realm of the unusual folk style, rather than something everyone is used to.
All works are copyright by yours truly, but may be distributed under Creative Commons Attribution Non-Commercial Share-Alike 4.0. That means, in short, you can use them yourself and your grove, and play the song to your heart's content both in private and in public, but must give credit where credit is due, and if you're planning on selling something involving this song we need to talk about that first.