 The area of present-day Iwaki was part of ancient Mutsu Province.The forms いわき, 石城, 岩城, 巖城, 巌城, and 磐城 are all ways of writing "Iwaki", which means "rocky castle".Under the Nara period Taika Reform of 645 AD, the central government formed "Iwaki district (磐城郡)" in the northern part of the present city and "Kikuta district (菊多郡)" in the southern part.