The etymological, philological, and grammatical side of the Slavic homeland, expansion, and contacts have been well described (e.g., Vermeer 2014; 2019; Timberlake 2013; Andersen 2003; Barford 2001; Gołąb 1991; Lindstedt and Salmela 2019; Nichols forthcoming gives an overview). The mechanism and sociolinguistics (both micro- and macro-) of the Slavic spreads and migrations have received less study and have not been su…