At first, Musashi called his swordsmanship style of heiho (art of warfare) 'Enmei-ryu' ('Enmyo-ryu'), however, in "Gorin no sho," he called it 'Nito Ichi-ryu' or 'Niten Ichi-ryu,' and 'Niten Ichi-ryu' is considered to have been fixed at last.
武蔵の兵法は、初め円明流と称したが、『五輪書』では、二刀一流、または二天一流の二つの名称が用いられ最終的には二天一流となったものと思われる。