I've been exploring this idea a lot in a guitar series that's meant to progress through as much of the technique as I had discovered at the time. I'd love to get some opinions and further ideas...
The Pluck and Chuck Series is the first playlist on the channel
https://www.youtube.com/channel/UCl3...88h_o50p5rW3nw
The AGF turned me on to John Martyn, who is quite the find! I'm just trying to find as many pieces of the thread as I can. If I have to guess, frailing banjo was part of the roots of the technique. Just a guess.