Does anyone know the phonological reasons for the alternation of the river name 'Narmada' as 'Narbada'? I also see this river name sometimes being spelled as Narbedda.

It is surprising to see a labial nasal winding up as an oral stop. Is there any historical evidence to believe in a transformation of narmada > narvada > narbada? /m/ > /v/ is very common in Dravidian, and /v/ > /b/ is common in the New Indo-Aryan (NIA) languages of East and Central India.

I appreciate any responses.

Regards,
Suresh.
Atlanta, GA.