Iron bone training?

What is this, what does it consist of? Sounded interesting, by name, but what is it really?

-Insert joke here-

sometimes it’s just too easy.

Iron Arm?

Not sure if this is what you are referring to, but in Hung Gar for example, training of Iron forearm, and Iron broom/leg is common. It is basically conditioning and hardening the desired area over a long period of time to become less sensitive to pain, and if done right, much less susceptible to damage, as well as increasing bone density and/or bone hardness. In laymans terms it basically turns your arms and legs into baseball bats.