@mjd "Hangul" always comes to my mind first because it's the way it's spelled in the official names of Unicode characters.
Apparently that block of Unicode has been there since the beginning, in 1991, so if the official change of spelling happened in 2000 then Unicode predates it.
Then again, I would have thought it ought to be possible to change the official names in a later version. (Surely there must be cases where that's _definitely_ needed, like someone made a straight-up typo that needs correcting.) But as of Unicode 17.0 last year, it's still "Hangul" everywhere – website, PDF code charts, machine-readable Unicode Character Database, everything.
Perhaps there's some policy about when a rename is permissible and this doesn't meet it?