Giving some particular construct in your language the official name "Concepts" is just unbelievably fucking atrociously stupid. Inexplicably greedy and needlessly destructive.
Say what you will about Haskell's user-hostile jargon, but even they had the sense to rename a concept that was originally called "Idiom". (now "Applicative")
(okay, I guess it might be worse than that)
Compiler writers often extend the language with new keywords.
I still feel like a standard container is less fundamental than keywords, but I value your perspective.
My original point was simply that std::vector, say, is just as good a "keyword" as any - perhaps, not because you cannot redefine it but because you wouldn't, and if you didn't like what it does, you'd use/implement something else.
It is in the same category of lies like C++ calling its thing a class. (except C++ does not try to have math background)
I prefer a common name to a wrong and confusing name.
Imagine how much more fun we could have had if they had "concepts" in the language back then!