No help here but here's Pete and Frank Warner discussing Proffitt and a brief clip of FP playing Going Across the Mountain at the '64 Newport FF from Pete's Rainbow Quest TV show.
I think the focus shifts to FP at about 23:20 in but the whole show is interesting, including Pete remembering a humorous letter that FP sent to a dulcimer maker looking for advice at 38:30.

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It's just speculation but the song could have come from earlier times and been rearranged to match the situation, that's sure been done before.You might be able to contact Clifton Hicks for more info.
At any rate it's a wonderful old song.