There is no direct English translation for "pohangina" as it's a unique place name. However, it is believed to be derived from the Maori word "pohangina", which means "to tear" or "to rip". This could refer to the river's powerful currents or its ability to carve through the landscape.
So, while there's no exact English equivalent, you can use "Pohangina River" or "Pohangina Town" when referring to the place.