Contagious Couplings, by Mark R. V. Southern, examines relationships between native languages and Yiddish. It highlights the historical and sociolinguistic development of Turkic, Iranian, South Asian, Slavic, Greek, Balkan, Judezmo, Armenian, Georgian, and Basque languages. One of the main focuses is on the adopted post-medieval and pre-modern Yiddish-speaking Ashkenazi homelands of Eastern Europe. The book emphasizes the role of ludic or playful modifications of a language's structures at the colloquial level as sources of linguistic change. And, it goes further to say that expressive language, linguistic iconicity, and etymological analysis can all complement and enrich each other.