Complex sentence: Western Yiddish originated in their culture, which emerged in the 9th century in Central Europe, and then spread to Eastern Europe, where it further developed, and eventually to other continents.
Split into simpler sentences: Western Yiddish originated in their culture, which emerged in the 9th century in Central Europe. Many centuries later, Western Yiddish spread to Eastern Europe, where it further developed as Eastern Yiddish, and eventually to other continents.