When carrying a lock on body, which statistical data and experiences to consider re: safety concerns With a custom-built bike in somewhat higher price regions, I now ended up with a high-security u-lock, which is also very heavy-weight. I also own a heavy-weight chain lock. For several reasons and specific occasions, it would be more practical to carry these locks on my body instead of attaching them to the bike.

However, when thinking about accidents, and the corresponding forces of heavyweight metal, and the comparative weakness of my bones, I would at least like to know which variant of carrying the u-lock (like corresponding holsters, in - or attached to - a backpack, ...) or the chain (over one shoulder, or like a belt, ...) has the least "damage expectancy". My research, among others with the German Cyclist Club (ADFC), did not reveal anything specific ... apart from the obvious, that any lock will damage your bones less if attached to the frame.
To be honest, from time to time I am even afraid of the keys in my pocket, should they take some funny stance on a fall and happily pierce through my leg/waist. But that's not what you asked...

I would take a look from the other side: assuming that there will be a hit, where would it be less dangerous?

I would say that a metal object hitting your abdominal area is not going to be funny: too many things that can get damaged: spleen, liver, kidneys, ribs, pick one. So, take out holding it around your torso.

Arms and legs are less dangerous, if you accept a broken bone or a concussion.

Probably safer is a backpack: the most plausible scenario in which you will hit your back is on a flip over, and in that case I hope you wear a helmet. The backpack itself might soften the blow.

I once happened to flip over (a branch got stuck in my front wheel) and luckily my backpack went between my face and the ground. But I just had water and food in it, not a metal object.