Answer
Rocker edited a periodical in London called "Arbeter Fraynd," which means "Workers' Friend" in Yiddish. Yiddish is a Germanic language spoken by Ashkenazi Jews, and it was the primary language of many Jewish communities in Eastern Europe and later in the United States. Rocker's periodical was intended to reach out to Yiddish-speaking Jewish workers in London and provide them with news and analysis of social and political issues.