If that's the case, the epithet would fit in the genre of Gallo-Greek votives made to The #Matres, like The Matres of Glanon and Namausos for example.

But De Bernardo Stempel considers it a #chthonic epithet:

"Given the Welsh comparandum annwn 'underworld', older annwfn from *an(de)-dúbno-, a pluralized feminine derivative *An(de)dúbn-ai with haplology still emerges as the most adequate reconstruction for this theonym, which may have meant 'The #underworld [mother #goddesses]'."