OK, there's nothing actually trivial about this. My mistake.
Here's the answer. The discription of St Brigit's birth is the Christianised version of the birth of Dawn. The sunrise, the birth over the house's threshold that symbolises separation of day and night, and the fire rising to heaven can leave no doubt about the function of this deity.
In
Indo-European cultures, the cow was the most revered animal, a symbol of wealth, of all that is good. The cow with red ears is a symbol of the reddish light of the sky at dawn.
Another deity that is connected with red cows is Ushas, the dawn goddess from the Rigveda, India's most ancient religious text, who releases red cows out of the (heavenly) pen at the beginning of every day. Here the red cow has the same meaning as in the Irish myth.
How are these two godesses connected? They stem from two cultures, Celtic and Indo-Aryan, who speak languages belonging to the Indo-European family of languages, and when analysing mythologies of other Indo-European cultures, such as Greek culture, we find Eos, which is also a dawn goddess, and like Brigit and Ushas she is also connected with red light (Eos is called
rhododaktylos Eos, "rose-fingered Dawn" in Greek), and Eos and Ushas in particular share many attributes, such as a golden attire, being white-armed, and a golden chariot pulled by two white stallions. Not only that, but the words Eos and Ushas, both meaning "dawn", stem from the same
proto-Indo-European word, Heusos (where H is a
glottal stop).
So, the two godesses, Brigit and Ushas, are the local versions of the ancient Indo-European goddess Heusos, or "Dawn", daughter of Dyeus, the Indo-European god of the clear sky and supreme deity. At the beginning of each day she opened the gates of heaven so that the Sun can rise, releasing the red light of dawn, and then yoking her stallions to the chariot and then riding out across the sky, the shining, burning spectacle of her appearance and of her horses and chariot heralding to the entire world the start of the long-awaited day.
I think it would be good now for somebody else to restart this game.
