Campbell, Mike Behind the Name. See also Xavier Delamarre, “Brigantion < brigant-,” in Dictionnaire de la langue gauloise (Éditions Errance, 2003) pp. 87–88: "Le nom de la sainte irlandaise Brigit est un adjectif de forme *brigenti… 'l'Eminente'." Delamarre cites E. Campanile, in Langues indo-européennes ("The name of the Irish Saint Brigid is an adjective of the form *brigenti… 'the Eminent'"), edited by Françoise Bader (Paris, 1994), pp. 34–40, that Brigid is a continuation of the Indo-European goddess of the dawn like Aurora.
