The article studies the possible relics that could confirm that some folklore motifs based on mythological traditions demonstrate some particular examples showing supernatural and chthonic features. Some of the cultural and linguistic remains of insular Celtic reflect contact with early non-Indo-European languages of the Atlantic region in the context of a Pre-Celtic substratum. One of the leading traces of it are the symbolic similarities of “red”, “black” and “white” between specific Celtic and Basque (Pyrenean) mythological and linguistic features.