An interesting discussion started last day with a friend of mine, a fine author, about what the Italian equivalent is of cold iron – as cold iron is well known as a tool against spirits, witches and demons.
The sort of thing that writers tend to notice, and file for later.
And it turns out there is no equivalent of cold iron because, basically, cold iron is plain old iron, but sharpened.

Francis Grose’s 1811 Dictionary of the Vulgar Tongue defines cold iron as “A sword, or any other weapon for cutting or stabbing.”

… says Wikipedia.
And Kipling, of course, used the expression to mean “weapon”.

But of course, when people that love reading and writing start discussing a topic, more and more things emerged.

For instance, it turns out that witches can’t walk across cold iron.
So it stands to reason that if you lay your sword across your threshold, no witch will be able to enter your house (through that door, at least). And believe it or not, there is this old tradition, in England – so they tell me – of burying a knife under the threshold.
Which is the sort of thing that pleases me no end – because it means that people acted, applied the logical extension of their beliefs.

And also, that’s the sort of fact that a writer of history likes to file away – because sooner or later it will come handy.

As for the Italian for cold iron, considering that ferro freddo gives me the creeps, I’d rather go for ferro affilato (sharp iron).
But that’s just me.