An instance of ‘Swahilization’ within the possibility domain involves the modal auxiliary verb -weza ‘can’. Assumed to originate from Arabic ‘ezz ‘power’, ‘azza ‘be powerful’ (Sacleux 1939: 1022; Nurse & Hinnebusch 1993: 294), it has spread further inland from coastal Swahili to other Swahili varieties, e.g. Bunia Swahili (Nassenstein & Dimmendaal 2019) or Maa Swahili (Drolc 1999), and to other local languages in East Africa, with attestations in Makwe, Kami, Bena, Digo, Nyamwezi and Matengo (Bernander et al. 2022). This study examines this two-staged transfer and the integration of -weza into Swahili and its further spread to other Swahili varieties and Swahilized local varieties.