Intransitive verbs and reflexive marking in the history of French

The Latin reflexive pronoun se famously developed into a middle marker in Romance languages. In this shift, it gained new voice-related functions (e.g. impersonals) and also became obligatory with some intransitive verbs, as in French s’évanouir ‘faint’. While the emergence of new valency-related functions has been widely studied, the obligatorification of reflexive marking remains largely unexplored. This paper begins to address this gap through a two-part study. First, focusing on Anglo-Norman Old French, we examine potential motivations for reflexive marking with intransitives. Second, using data from several Gallo-Romance varieties, we test the hypothesis that intransitive reflexive marking was originally optional — e.g. (se) gesir ‘lie down’ — and that only some verbs later became reflexive-only. Our findings suggest that, although obligatorification likely mattered, reflexive-only verbs arose through a more complex interaction of factors. These results also inform the diachronic typology of middle markers by clarifying pathways to middle-only verbs.