It's interesting that the first recorded uses in English (according to the OED) mention it as a Turkish foodstuff:
"1625 S. Purchas Pilgrimes II. ix. xv. §9. 1601 Neither doe they [sc. the Turks] eate much Milke, except it bee made sower, which they call Yoghurd."
(See also[1]) I suppose it's possible that Bulgaria got yogurt during Ottoman rule in the 14th century, and that the research in the early part of the 20th just happened to be there. But it seems more likely to me that any group that kept animals for milk would have fermented the milk to make it last longer, and that knowledge would have traveled all over Eurasia.
There may have been no real disambiguation by the original author from "Turks" as an epithet for Ottoman citizens and specifically ethnic Turks as well.
"1625 S. Purchas Pilgrimes II. ix. xv. §9. 1601 Neither doe they [sc. the Turks] eate much Milke, except it bee made sower, which they call Yoghurd."
(See also[1]) I suppose it's possible that Bulgaria got yogurt during Ottoman rule in the 14th century, and that the research in the early part of the 20th just happened to be there. But it seems more likely to me that any group that kept animals for milk would have fermented the milk to make it last longer, and that knowledge would have traveled all over Eurasia.
1: https://www.bonappetit.com/test-kitchen/ingredients/article/...