Oh well. I've done more research and am now thoroughly confused. Essentially I think this is a version of a herringbone stitch done vertically instead of horizontally. Interesting trying to chase this down.
Anyway. I managed to finish this stitch last night. I've got some couching with herringbone to do today. And some backstitching. And then the piece will be finished. I like it more and more the closer I get to the end of Arabella.