I'd say it's pretty definitely made from a leaf spring, especially with your comparison picture. It's kind of like finding something made from a wagon tire; the shape of the metal kind of tells you what it had been at one point.
With that in mind, I'd hazard that the hole at the end of the tang is the original bolt hole of the spring pack, squished rectangular when drawing the tang out. At the same time, knowing how much it would have closed up the hole to forge like that and seeing how it bulges around the hole, some effort was made to keep it open with a punch or drift.