Writing and etymology in Korean
鋼 (강) – steel
鐵 (철) – iron

Tigers subject their cubs to brutal trials and instill harsh discipline so that, once they reveal their wild nature, they become true kings of the mountains. Similarly, steel becomes more resilient and stronger after hardening.

If a blacksmith has a piece of hardened steel, he must strike it evenly. He must forge the steel both day and night to create the necessary condition and give the metal the ability to withstand all four seasons. Morning is like spring, day is like summer, evening is like autumn, and night is like winter.

In the same way, we go through four seasons, or four periods of life: first comes childhood, then adolescence, then adulthood, and finally, one reaches old age. The more intensive and longer we forge our steel during life, the more hardened it becomes. We have to work as hard as we can to forge it.