Modern linguistics not only wants to describe, it aims at explanations and predictions based on linguistic theories. The extension of linguistic theorising to vernacular data is a contemporary enterprise much in vogue. Vernacular data are a valuable testing ground for established theories of language and an indispensable corrective for our assumptions about universal properties of languages. The study of vernaculars prots from this enterprise by gaining access to new methodologies, hypotheses, motivations, and explanations.