*Oysya, you oysya,
Do not be afraid of me,
I won't harm you,
Do not worry.
That's an old folk song of Terek Cossacks, written to the melody of the Caucasian **lezginka. It was written presumably during the Caucasian War of the XIX century.
*There's a few versions of origins of that word "Oysya".
1. "Oysya" is the word of the Cossack jargon of the Vedic (Old Russian) language. The word consists of the interjection "oy" (eng. "oh") and the suffix of "sya" (eng. "-self").
2. "Oysya" - is how Terek Cossacks mocked Caucasians (Chechens, Dagestanians, Ingush) word "assa". Which in its turn is a whoop which they do when they dance their national Caucasian dance called Lezginka, to inspire dancer.
3. The word "Oysya" is how the Terek Cossacks called Vainakhs (Chechens and Ingush people). When they danced lezginka - they shouted guttural cries "Horsa!" (or "Hosa!"). Which is they got this nickname.
**lezginka - https://youtu.be/naKcUWaqqyk