Cold Iron

I just heard a rather interesting thing. Cold Iron has long been known for metaphysical properties, such as being bane to certain types of fae and their magics... it's also one important part of the so-called "secret of steel", which many ancient cultures prized highly for obvious reasons. But I heard, today, a christianized take on the powers of cold iron. One rather unique and almost surprisingly logical. Iron was what was used to pierce the hands and feet of their incarnate god when he was crucified in their mythology, and it's properties supposedly stem from that.

I don't personally subscribe to this belief, but I note it because it's one of the few modern christian explainations of the metaphysical I've heard that isn't borrowed mostly intact from an older pagan source. That intrigues me... I wonder who the notion originated with? And how much acceptance it has within the christian mysticism movement?