The poem refers to the practice of katasogi 片削ぎ which was used in the construction, or reconstruction, of Shinto shrines. When constructing the roof of a shrine, the chigi 千木, which are crossed beams protruding above the roof at either end, were shaved (katasogi) into the appropriate shape (click here for more information about chigi and shrine construction), and by using the term Kei’un reinforces the Shinto imagery of the poem.