The Emperor (Kammu) issued an edict as follows. I understand that the topography of the proposed site is really in accordance with the report. This location is guarded by mountains and rivers just like collars and sashes. Based on the good topographical conditions, the name of the Yamashiro Province (region behind the mountain) is to be changed as the Yamashiro Province (castle of the mountain). The people who are gathering around the new capital adoring the Emperor’s virtue call the new capital “Heian-kyo (capital of peace)” in chorus.

— Nihon-kiryaku quoting from Nihon-koki, 8th day, eleventh month of the Enryaku era (December 4, 794 AD Julian)