[@Lyla] Mmm, good points. 

I would think that maybe some wizards came up with it by gathering a good many verbal magical spells from the nation's libraries and other sources as an experiment, and by trying to synergize them into a language through generations of study they would be making an attempt (at best) to mimic or re-create a theorized (and "supposed") "Original Magic Language" they think very ancient wizards or such possessed in the beginning or something of the sorts. But since the current magical language origins are largely unknown with only rumors existing, they cannot recreate the actual "original" magical language or whatever they are aiming for, instead creating a pesudo-magical language that was infused into the character's brain via magic or was taught to them and such in an attempt to create a "world's most potent wizard" or something of the sorts as yet another experiment to see if the language they created would actually work. 

But that's perhaps just a bit of speculating how to make it work on my part.

I would say that perhaps the magical language also drains the user physically when used, so casting large spells like covering a city in a thunderstorm would possibly cause them to pass out cold in the process due to the sheer strain of creating such a large phenomenon. Would that be a possible idea for a drawback? I am open to suggestions as well. :)

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On a side note, does necromancy exist in this fictional universe?