Yes, maybe it is not well known in Russia (I am guessing you are Russian) but Cyrillic originated in Bulgaria. I immediately recognised this since I was fascinated by ancient greek script due to its' wide use in mathematics.

I am guessing that this also is almost identical in Russian, since it uses old words and words that I already knew were common between the languages. Russian and Bulgarian share a lot of the most commonly used words. Personal pronouns, forms of the verb to be, and so on. When spoken, the similarities are hard to miss also, although in Bulgarian it is said 'Zashto', but generally it sounds the same way as the russian with a hard start to the SH sound like transliterated into english 'Shto'.