Something that's been on my mind lately is very similar to this. It's how terms I could have sworn originated in our circles have somehow became co-opted and redefined before entering the mainstream. Let me explain:

I used to be active on the TRS forum around 2016. And there I could have sworn that people used the term 'woke' to refer to 'having awakened to the Left/System and becoming very Right-wing in response'. Several years later I heard a quackademic using the term 'woke' to refer... to herself. But this woman wasn't even remotely 'woke' in the sense I understood it. She's a White bisexual in a relationship with a literal Jew. One of her quackademic friends is an openly Antifa lesbian. Later I started to see it online. By late 2018 'woke' had developed its current meaning. Nowadays 'woke culture', 'wokeness', 'wokesters', etc. are ubiquitous terms even in the mainstream 'Right' media.

And what about 'based'? It used to mean something like 'that sounds very Right-wing and that's good'. Now I've seen literal feminists use it to mean something like: 'that sounds very feminist and that's good'.

And what about 'redpilled'? Now I see literal feminists using the term 'pinkpilled' to mean 'I became aware of the "patriarchy" and am now committed to feminism'.

The one I'm most sure about is the current term 'cuck' which, I could have sworn, came from the Alt-Right term 'cuckservative' around 2015-16 to mean: 'person who claims to be Right-wing but is insufficiently so, who heavily and weakly compromises with their opponents, to the point that they are in practice Left-wing'.

Now I see literal Far-Leftists use 'cuck' to refer to people who are insufficiently Left-wing (e.g. the viewers of 'Vaush' or 'Destiny').

Did these terms originate somewhere else first, and I'm just getting the origins wrong? Or are they really our terms, having drifted away from their creators to develop new meanings, with every Leftist and 'normie' out there completely unaware of their origins?

Returning closer to your original point, I've also noticed that various terms that cannot really be co-opted by other groups ('White genocide', 'Great Replacement', 'Cultural Marxism' being three of the best examples) have undergone a somewhat similar change, whereby instead of developing new meanings, they are simply branded 'conspiracy theories', etc. and became taboo. 'Good' people apparently do not mention or believe in such things. Mentions of 'Cultural Marxism', for example, inevitably attract some smug Cultural Marxist who will proudly mention something about the supposed 'Nazi' origins of the term—a transparent attempt at guilt by association.

Likewise, despite the 'Great Replacement' having become taboo, terms such as 'replacement migration' effectively mean the same thing, except in language that the System accepts—'replacement migration', far from problematizing it, frames it as 'necessary' and even 'desirable'. Thus we have an example of a term that appears to be taboo for little reason other than its 'Far-Right' origins, whilst newer terms have been invented to replace it simply because it seems that there must be a term to refer to this very real phenomenon.

Similarly, 'White genocide' was effectively replaced by a term that means the same thing, except in a mocking, non-critical and non-serious way: 'Mayocide'. Again, it appears that people accept that 'White genocide' is real, but have simply invented a replacement term which is essentially supportive of it ('White genocide' clearly problematized this very same phenomenon, which is why it needed to be replaced).

We can, of course, also see the System/Left co-opt and create other terms ('peaceful protest' is constantly used to 'de-problematize' violent, destructive Far-Leftist riots, which makes the crushing of such riots seem more unjustified in the eyes of the masses, helping to ensure that there will be no crackdown on them).