Why are there two Japanese readings for a Korean word?


Leaving aside the issue of whose world view is correct, there seem to be two
Japanese readings for the Korean word for the body of water between the two
countries:

NHK writes 東海 【とんへ】 but wwwjdic writes 東海 【とうかい】

アメリカ軍【ぐん】「日本海【にほんかい】を『東海【とんへ】』と書 【か】いたのは間違 【まちが】い」

_U.S. military: "Writing 'East Sea' for Sea of Japan was a mistake"_

<https://www3.nhk.or.jp/news/easy/k10012936691000/k10012936691000.html>

Why are there two Japanese readings for the Korean word? Are they
interchangeable and equally acceptable as readings of the Korean name?




In both languages the word is formed of borrowed Chinese elements, which after
borrowing went through several changes. トンヘ is the Japanese approximation of
the Korean pronunciation, while とうかい uses the on'yomi (Chinese-derived)
pronunciations of the characters that are common in Japanese.




In both languages the word is formed of borrowed Chinese elements, which after
borrowing went through several changes. トンヘ is the Japanese approximation of
the Korean pronunciation, while とうかい uses the on'yomi (Chinese-derived)
pronunciations of the characters that are common in Japanese.

