While CV has one definition of fit as the edge or hem of a sock, knitted
things, etc as well as fitja upp to begin knitting,
it seems unlikely one would actually have shoes made of nalbinding.
More likely it is the idea of shoes made of "fit." One of the definitions
of "fit" is the leg parts of the hide - - perhaps because of the natural
shape of the back leg or for some symbolic meaning which the biblical
reference in CV suggests.
http://www.northvegr.org/vigfusson/155.php
Grace
Fred and Grace Hatton
Hawley Pa