As there are 12 names for each clan - 12 for Veena, 2x6 for Rava - my guess is that they don't refer to something alike to tia/nunh but instead to region or something else. Veena and Rava share a lot of culture except for their following of the Green Word and locale. There's a chance the Djt- or Rehw- prefixes on Rava names refer to whether they follow or have broken the Green Word, but as all PC Rava men have by definition left Golmore (and thus broken it), it makes no sense for it to be an option.

There has to be some significance around there being 12 names, I think. Given how closely related they are (in the case of Veena) as well as how restrictive, it only makes sense that it defines them along a category that can be split into 12 or 2x6, so... regions, birth months, something like that. Keep in mind that ordinarily Viera men would have very little use for a surname since they belong to no village and meet very few people. It makes sense, then, that their surname is a utility used by women when they do visit a village. Guess we can only know for sure when they tell us, but it's food for thought.