https://www.dictionary.com/browse/terrible
3. exciting terror, awe, or great fear; dreadful; awful.
4. formidably great.
I think it's a perfectly suitable name for a warship. The notion of "terrible" describing the inferior quality of something is a much more recent meaning, I believe.
Especially considering the British colloquial usage of "fanny" I think someone was in a particularly good mood that day.
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https://www.dictionary.com/browse/terrible
3. exciting terror, awe, or great fear; dreadful; awful.
4. formidably great.
I think it's a perfectly suitable name for a warship. The notion of "terrible" describing the inferior quality of something is a much more recent meaning, I believe.