A cross-linguistic rarity in synchrony and diachrony

This article shows that a hitherto unattested construction type - namely, adverbial subordinator prefixes - is in fact attested in several languages. While Dryer's 659-language convenience sample does not turn up any clear example of such a construction, we argue that this is in part due to arbitrary coding choices that a priori exclude potential constructions of this type. In order to document the existence of adverbial subordinator prefixes, we present a number of languages with different genealogical and areal affiliations, each of which shows solid synchronic evidence for what appears to be a universally dispreferred feature. Furthermore, we identify some diachronic pathways through which adverbial subordinator prefixes grammaticalize.