The process of naming is an extremely powerful aspect of language. When we name something, we differentiate its essence from things which are not-the-thing-named. Thus, we are used to thinking of, for example, a knuckle as separable from the rest of the finger; the finger as separable from the rest of the hand, and the hand as separable from the rest of the body. By naming it, we give the knuckle existence. This process is called entification: to consider as, or cause to become, an entity.
However, we have names for things which are somewhat less concrete. For example, where does your lap go when you stand up? Can love exist independently of the lover and the object of that love? These mistakes are examples of reification: to treat (an abstraction) as substantially existing, or as a concrete material object. Mistakenly believing that, since there is a word for something, it must therefore exist is an example of the pathologies of language that Wittgenstein warned of. Consider, for example: does “forgiveness” exist? What if you only spoke one language and there was no word for “forgiveness”? In the “real” (objective) world, does forgiveness exist or doesn’t it? The question is a non-sequitur, and it cannot be answered reasonably.
Now, what if your language did not have any first-person pronouns? What would you make of Descartes' famous expression “I think, therefore I am”?
“Verbal chicanery. A trick of words,” He spat. “You say ‘I think’ and therefore there must be an I that thinks – but if I said ‘the heffalumps are coming,’ you wouldn’t take that as evidence that they exist, would you? Why should you accept that you exist just because you hear yourself talking?”
Steven C. Shaffer — Judgment Day: Filing an Appeal
And so, I suggest to you that “God” is not God. “God” is a word and as such it is arbitrary. God exists, just like forgiveness does – but don't get lost demanding evidence of the reified version of either of these.