The source of the 'Shugan-mei' seems to be a Buddhist monk, and Shugan-mei refers to the swords with a specific mannerism of Chukichi with his signature inscribed on a sword by imitating the letters written by this monk.
秀岸というのは僧侶らしく、この人の書く字を真似て切った癖のある切銘のことを言う。