Leading up to the Heian period, it was generalized that a government office of the Kokushi (called Kokucho [local government]) itself was called Kokuga and the Administration and Judiciary structures of the Kokushi were called Kokuga.
平安時代頃までに、国司の役所そのもの（国庁という）を国衙と呼んだり、国司の行政・司法機構を国衙と呼ぶことが一般的となった。