Dear of troy: I learned "punka wallah" from Kipling, meaning the flunky who lazily waved a big fan give air movement in the rajah's rooms.
I think that may be source for other uses of the word. I too thought at first the "kelawalla" was a fruit peddler, but could find no confirmation thereof. And I could find nothing for "kela" either.

A change of search words yielded:
' Bananas (kela) of one sort or another are also on sale all year round, '

Dear Shanks: is a walla also a wallah?