It may refer to a type of silk fabric. Such as dupioni, which is thicker than typical silk cloth, and it is iridescent, consistent with the description as being 'garments of light'.
Leolaia:
Also the word basilikos "royal, kingly" comes to mind, and royal clothes would also make sense in the context.
A shiny silk cloth in those days would be expensive, so it would be appropriate that they might use a word associated with a base word related to royalty for such a cloth.