The phenomenon of unrounding ö and ü is not restricted to Yiddish, it also occurs in many German dialects, Silesian (both Upper Silesian ans Lower Silesian) is one of them, but also Rheinfränkisch, Moselfränkisch, and Obersächsisch show this phenomenon.
P.S. The unrounding also affects the diphthong eu/äu which is unrounded to ei/ai (pronounced IE).
More one this (in German):
https://de.wikipedia.org/wiki/EntlabialisierungThis message was edited 10/20/2024, 9:37 AM