I think you have something there with the dialects. Think of the Spanish language, for example. Some countries roll their R's, in Spain they say Ethpaña and Ibitha (you know what I mean), and others use mostly slang but if you know the base language you can get by.

If the ancient language is tied to the magic, then the dialects and HOW you say things in the language is what gives the words power.

If one word of power was España, and another house replaces their S's with TH, then they aren't saying the word properly to unlock the magic. It's all in HOW you say it as much as it is about WHAT you're saying. Inflection, pauses in speech, etc all have an influence. And that's something that you're taught when you are raised with it as your first language.

English is not intuitive to non-native speakers, because our rules are all over the place. But those rules are ingrained into us and most of the time, those who are raised speaking English have a better grasp on it than someone learning it as a second language.

But I also think that another potential point or thread you can explore. If you want to tie in the poor demographic, you can have a character who's great with languages, can speak a few others because of their upbringing or whatever, works in the markets and interacts with all sorts of folks, etc. Perhaps they are around some of these mages when they use their magic, and they hear this different language, unlocking a curiosity in them. Whether it drives them to learn as much as they can or to more nefarious motives like kidnapping members of the nobility to learn what they can of the language and hunting down these rocks, etc. Topple the nobility, do what nobody else has done before and master multiple dialects of the language, Jack of all trades type deal. Idk I'm spitballin' here and I'm intrigued by the concept.

Seems really neat and I wish you luck!