According to Celtic Myths and Legends by Peter Berredsford Ellis Brigid, or Brigantu, is not the daughter of Dagda. Rather they were both giant acorns dropped from the tree Bile. From one acorn sprang Dagda and the other was Brigid.
Surprisingly this is not in name days on February 1st in Ireland as Saint Bridget's day, also known as Imbolc, the halfway point between the winter solstice and the spring equinox. https://en.wikipedia.org/wiki/Imbolc.
From "Breo Saighead", "The Firey Arrow", Brighid means mainly "The Strong and Exhalted One", but has been translated as "She Who Exhalts Herself", "The Firey Arrow", or just "The Exhalted One".