It is curious that one never sees cīna used in Tibetan materials until comparatively late times. The ubiquitous
Tibetan term for China is rgya-nag, though from about the 10c. on one also sometimes sees stong-kun,
(presumably from Ch. dong jun ?|?? or dongjing ?|京 though there is some controversy about this). Rgya-nag is traditionally said to mean the "black expanse," referring to the realm in which people wore black clothes, however,
I suppose that it might also come from 支那 -- one would have to go back to the Middle Chinese phonology
to be sure that this is plausible. If so, then the Tibetan evidence would argue for this hypothesis and against
Qin as the sourse-term.