"Ken Zen Ichinyo" is a phrase to express the close connection between Zen and swordmanship. However, both are originally separate. I analyze examples of Zen terms quoted in the Heihokadensho of Yagyu Munenori, and consider The Mysterious Record of Immovable Wisdom of Takuan who was an adviser of Munenori next, thereby clarifying the source of the expression "Ken Zen Ichinyo." There were two intentions in the way Zen terms were quoted helping us understand the origin of "Ken Zen Ichinyo."