In his discussion of Roman wind-names, Seneca the Younger employs a striking metaphor to describe the integration of the name of the south-east wind, Eurus, into Latin. The name Eurus, Seneca says, has been ‘granted citizenship’. This is one of six instances of the metaphor of ‘granting citizenship to words’ in surviving ancient texts. In this article, I use this metaphor as an entry-point to reconsider the importance of citizenship and language to ancient conceptions of Roman identity and status. The metaphor is revelatory of ancient thinking about what citizenship meant, what it depended on, and to whom and on whose authority it should be granted, questions that became urgent as citizenship spread across the Empire. Different versions of the metaphor offer tellingly divergent views of citizenship and of language. These reflect the tensions between origin and culture, inclusion and exclusion, cosmopolitanism and nativism, in contemporary notions of what it meant to be or belong as Roman.