Swahili

As I'm backdating all the t'ings I'll ask - when did the Swahili start up? That's the Bantu-based trade tongue along Mozambiq up through Nairobi-ish. Clearly nobody's speaking that before the Bantu showed up.

Ezequiel Koile et al have a chart. Its enumeration is... odd: for instance 14 goes to 12,13. Relevant here 14 also goes to 22,23 whence 18,19 on that eastern coast.

This is all East-Bantu so after 1000 BC. Alongside Fig. 2, we learn that 22/23 split from 18/19 more like 400 BC and then 22 and 23 split perhaps in the 200s. So: the Bantu had iron.

We're coming right up to the Hellenistic Era, here; and soon, the Parthians. It's all before the Late-Antique crash. When the first Greeks (or Yemenis) came south, they conversed in Swahili.