Theoretically, there are no kossith just like there are no real Gauls anymore.
Yet I can go to France and find you French people singing songs that mention the Gauls, as well as buildings that bear their name, and the symbol of France is the Gallic (Gaulish) rooster.
Obviously, though I will agree the word is not in the most common usage, but look, here it is 2000 years or so later, and it's still around.
I also guarantee you that most Frenchmen will know what you mean if you use the word "Gauls". They might look at you funny if you call
them "Gaul," but probably not as angrily as if you call them "Frog".
It is a culture that no longer exists.
The Qun seems to have destroyed that culture, much as Islam seems to have wiped out the pre-Islamic culture of Arabia. Well, actually not, as you will still find many pre-Islamic customs among Arab people.
Suffice to say, there is no term that describes the species of the giant sometimes horned metallic skinned people that make up the majority of the Qunari culture.
Maybe not a word that's used in-game by anybody other than a few Thedan scholars and antiquarians who we will never meet, but guess what, there's a word that works just fine on the forums.