Mongolian Wikipedia has an article on:

Болгар

Wikipedia ^mn

Derived from Russian Болга́рия (Bolgárija).

• IPA^(key): [pɔɮ.ɢäˑr]
• Hyphenation: Бол‧гар

Болгар • (Bolgar)

1. short for Болгар улс (Bolgar uls): Bulgaria (a country in Southeast Europe)

   Монгол, Болгарын харилцаа ― Mongol, Bolgaryn xarilcaa ― Mongolia–Bulgaria relations

This proper noun needs an inflection-table template.

Judging by the first vowel, most likely borrowed from Carpathian Rusyn болґар (bolgar), болгар (bolhar), ultimately from Old Church Slavonic блъгаринъ (blŭgarinŭ).

• IPA^(key): [ˈbɔlɦar]
• Rhymes: -ɔlɦar
• Hyphenation: Бол‧гар

Болгар (Bolhar) m pers (feminine equivalent Болгарка, related adjective болгарски)

1. Bulgarian (a native of Bulgaria)

• Medʹeši, H., Fejsa, M., Timko-Djitko, O. (2010) “Болгар”, in Ramač, Ju., editor, Руско-сербски словнїк [Rusyn-Serbian Dictionary] (in Pannonian Rusyn), Novi Sad: Faculty of Philosophy
• Fejsa, M., Šlemender, M., Čelʹovski, S. (2022) “Bulgarian”, in Анґлийско-руски словнїк [English-Rusyn Dictionary] (in Pannonian Rusyn), Novi Sad: Faculty of Philosophy; Ruska matka, →ISBN, page 45