However, for such an old word/idea, I’m quite sure it was taken from a Chinese text, as even today, when certain classical words or ideas are sought, it is a common practice to quote Chinese sources. I think it’s somewhat similar as to how in English, when we are looking at the etymology of a word to further understanding of the origins, we look to see if there is a similar Latin word which it was based on, except we don’t just simply copy that definition as the Japanese and Koreans have done.

In Tokugawa Japan, by contrast the same ideogram, read “koku”, usually referred to the local province or domain. It was not until after the Meiji restoration that the Japanese started to use “koku” and its compounds as a terms referring to the nation state. A lot of Chinese nationalists in the late nineteentheth and early twentieth borrowed (or reappropritated) Sino-Japanese compounds with “koku” such as “kokusui”, “kokugaku”, “kokugo”, etc., infusing them with Han Chinese nationlist connotations. Where Korea fits into the picture I don’t know, but I wouldn’t be surpirsed if the Korean story shares many elements with its Chinese counterpart.

Just my two cents…