Thanks, Mick, for another very helpful post.

However...

A search of the hundreds of millions of pages available through Google Books back to before 1800 shows only *one* example (aside from Abbott/Fowke) of "Indian buck" as some sort of food. Nor does it appear the HathiTrust Digital Library or in the various newspaper databases I've consulted, including one devoted to the Civil War.

Nor does "Indian buck" appear in either the OED or the English (including Hiberno-English) Dialect Dictionary.

And the *one* finadable example is Keneally's (writing in 2010)!

It *looks* as though he came upon "Indian buck" in the song and, puzzled, jumped to the conclusion that it meant "maize"; or that his source (not listed, so far as I can tell from Google Books) had jumped previously to that conclusion.

Of course, the song's writer, straining for a rhyme, might himself have invented "Indian buck" as an ad-hoc synonym for "Indian corn" or, in his own mind, "tough Indian venison taken from buck deer." Either would easily explain the dearth of other examples.