invaluable? I suppose the etymology may be that something invaluable is so important that any value ascribed to it still does not approximate its true worth.

That is interesting. Something I've noticed is that if you believe that words should be defined in such a way that they are logically consistent with other words, it's possible that there are words that literally everyone uses incorrectly. And under this paradigm, there are many words that mean the opposite of what they 'should' mean. As far as I know though I'm the only one who believes this, although it wouldn't surprise me if other people have explored the idea before.

For enantiodromes, I recommend 'anathema', which was once a thing devoted to the gods but came to mean accursed, and 'cleave' which still occasionally means 'adhere to' but more commonly means 'to split'.

It's interesting (and frustrating) when this phenomenon appears across different languages. The French 'pas terrible' means not very good rather than not terrible.

Didn't the words "objective" and "subjective" switch meanings some time ago?