Well, the opinion of the scholars is divided on this issue, but the majority of them, the most knowledgeable in fact, agree to the fact that this is not a derivative of any other infinitive. This word Allah is a proper noun for God, and ilah is the word commonly used for any God or concept of God, but the real God is named Allah. So the Holy Quran gives the attributes of Allah to define the personality of Allah. And Allah remains in a way without meaning, but when the whole halo of the attributes is built around it, then Allah acquires all the meanings that the attributes refer to.
