Origin of "Fierro" surname?

-So I read the question about the "del fierro" surname on here and one would say without a doubt that it is a Spanish last name. According to the Spanish National Statistics Office (http://www.ine.es/daco/daco42/nombyapel/nombyapel.htm), the region with the greatest amount of people with the surname "Fierro" live in Leon and there's a total of roughly 2300 persons with the surname in all the country.

However I found a very similar website to the Spanish National Statistics Office, but Italian(\http://www.gens.labo.net/it/cognomi/).Apparently there is an equal amount of persons with the last name in Italy as in Spain.

So where did the last name (Fierro) really originated at? Could it be the spanish equivalent of italian Ferro? Help me out here guys.