Slavic -osh suffix

There seem to be competing etymologies of the Slavic personal name forming suffix -osh, as in Polish Milosz or Serbian Uroš.
I've heard it might be paleo-balkan as it is present in both Albanian and Romanian in some form, and it also figures in lot of Hungarian words.

Paleo balkan etymology seems unlikely to me as the suffix is very common outside the supposed area of the substrate. I am not aware if any name formed this way predates the settling of the Hungarians on the Panonian plane

Are Slavic sound changes able to effect this form from some PIE morpheme, and if so is such a morpheme attested in any other IE language?