Since I've been trying to build a fantasy based world where magical energy exists but you can't just use magical energy directly. You need spells and catalysts.

But this put me into the thought, how do these spells and the complete system even come into existence. Like the words who decided that, a particular word ignites flame or a particular word opens a portal to a particular distance. How the hell do the words and symbols even gain meaning?

You may say i can add imagination and then add magical energy into it but then how will it create huge tier spells where the mage doesn't know stuff about the world and the imagination doesn't even make sense.

You may say the symbols and words were created by a former god or dirty but how TF did that God do it? How did he manage to make some system when there was no reference to it at all?

So now I'm planning to make a world where new magic systems can be made by anyone, then what do u think the criteria should be? How do I define the criteria? Any ideas?