On the Russian article of Iosif Unshlikht it says he was born into a rich Polish-Jewish family in the biography section so I assumed it was Yiddish. I could be wrong but that's what made me think it was Jewish.
https://ru.m.wikipedia.org/wiki/%D0%A3%D0%BD%D1%88%D0%BB%D0%B8%D1%85%D1%82,_%D0%98%D0%BE%D1%81%D0%B8%D1%84_%D0%A1%D1%82%D0%B0%D0%BD%D0%B8%D1%81%D0%BB%D0%B0%D0%B2%D0%BE%D0%B2%D0%B8%D1%87