五郎入道正宗 Gorou Nyudou Masamune

What is Gorou Nyudou Masamune in Japanese Katana terminology?

Gorou Nyudou Masamune is one of the most famous swordsmiths, often synonymous with Japanese swords. He was active from the Nanboku-cho period to the Kamakura period and had many disciples, including the "Masamune Juttetsu". He is said to have established the major school of swordsmiths, "Soshu-den".