Mhm, well generally I would try to name something that is hard after something that sounds hard? Like,the cold itself is not soft. It comes, not slowly, but very fast and basically feels like a bite in your hands, so you say "kalt", like the bite it does to you.

But iron/Eisen appears hard and cold as well but is named something so soft. I think that is a bit unusual, though I'm sure there are a lot of other examples. But it is a good kind of unusual. You could soften iron while heating it, but even non-scientifically, you can therefore think that even if something appears to be hard, it can have a little softness around it - and may it be just a name.

And I think that is odd in a good way :D (is odd usually used with bad things?)