An means “peaceful” and go means “reside.” Ango means the ninety-day summer retreat. In India, the rainy season lasts for about three months in the summer. Buddhists in ancient India used this time for concentrated practice of Zazen, and this period was called varsika in Sanskrit. The tradition was imported into China, and so when Master Dogen went to China he experienced the concentrated practice of Zazen for three months in the summer and felt his mission to introduce it into Japan. So he wrote this chapter.