*incoherent rambling* 
Kossith is the name of the species of bronze-skinned, horned giants that form the majority of Qunari. Qunari don't pay attention to race, so almost no one in Dragon Age uses that term for them anymore.
What we know from Bull and others is that the Qunari fled the kossith and came to Thedas, rather than the previously assumed 'They're a vanguard of a whole continent of Qunari'.
I believe Par Vollen is an island.
But we don't know what lies beyond on the map, and the maps don't usually show all of Par Vollen.
Regardless, it seems the Qunari sailed in from the northeast of Par Vollen.
The Antivan merchants who are sailing too close to 'Those Beyond the Sea' seem to be exploring east from Antiva.
The Qunari Elf connection is due to Corypheus referring to Qunari Inquisitors as a 'mistake, blood gorged on corruption', Kieran saying that Qunari have blood that isn't theirs, Bull sharing Ben-Hassrath theories that the Tamrassrans added dragon blood to the Qunari to make them stronger, Solas being very insistent that Qunari are blood-crazed beasts despite the fact that the stereotype of Qunari is freakishly logical and methodical, and the mosaics which appear to have Qunari centuries before they showed up.
Then there's Liz's comparison of dwarven casteless brands, vallaslin in Arlathan and the Dalish clans, and the Qunari practice of vitaar. All of which suggests a common link.
My theory is that the kossith were originally genetically messed with servants of Elgar'nan. The pyramids in Par Vollen portray horned giants serving the gods, and they're designed to match up to the Sun constellation.
I'm really hoping the kossith are the patient warriors of Elgar'nan waiting for his return.
Does that help? 
I, um, definitely don't ramble when I get excited.
