When Jerry Siegel wrote his K-Metal story in 1940, he did not give it a title. Each page of surviving artwork is merely labeled “Superman” across the top, in pencil.
When we started our reconstruction efforts back in 2003, we gave the story the name, “The SECRET of the K-METAL“:

Two years into the project, I happened to come across and read Gerard Jones’ book, Men of Tomorrow. In it, he invents and assigns the name “K-Metal from Krypton” to the story. This is an anachronistic and unofficial title, but at the time, I liked it— so we put it all over the website, and in all the articles on the website, and made lots of promotional graphics displaying that title. If we had not done that, and had not promoted that name, it is very likely that few people would have ever been aware of the term “K-Metal from Krypton,” or if its use in Men of Tomorrow; let alone even heard of that book. It was from our website that the name “K-Metal from Krypton” spread and became the defacto title of the tale; people throughout the world now assuming that’s the actual title of the story.
But it isn’t and it never was.
When we learned about Gerard Jones’ arrest and conviction and of the morally abhorrent nature of his crimes; we were completely shocked and stunned. We have deep sorrow and regret for the role we may have had in popularizing and spreading his assigned name for the tale.
We have reverted back to our historically inspired, original name, “The Secret of the K-Metal”, and ask that others consider doing the same.

It is believed, although not confirmed, that DC Comics’ in-house name for the story is simply “K-Metal.”
The terms “K-Metal” and “The Secret of the K-Metal” first appear in the novella, The Copper-Clad World, by Harl Vincent; published in the September, 1931 issue of Astounding Stories magazine.
Jerry Siegel was about to turn 17 years old when this issue was published.