By Dr. Tony Garland
Q. Where did the word Allah come from? I've heard the many names for our God, but never Allah. Is the Allah of Islam the same as the Allah of Arab Christians?
The word Allaah is not a new and unknown word and name. It is a word and name used for the Creator by past prophets and Messengers of the Creator. The Arab Christians use the name Allaah for God and Allaah is also used as the name for God in Arab Christians' Bible. Also Allaah is not some "moon-god" or "god of the Arabs" as some Western authors have falsely attributed to Islam. Allaah is the One True God, Who is the Creator, Unseen, Who has Power over everything. He is the God of the prophets and Messengers; Noah, Abraham, Moses, Jesus and Muhammad (Peace be upon them all.) All of Gods' (Allaahs') prophets and Messengers came with the same message that mankind should only worship the Creator Allaah alone, and to not worship others besides Him or ascribe partners to Him in worship (ie. saints, sons, crosses, etc.).
A. Answering the question of the origin of the name Allah goes as deep as the various experts. Although I have some information on this subject, I'm not well-placed to put forth an authoritative answer on the origin of the term. However, I would like to cut to the chase and address the claim implied in the quote above: that the Allah of Islam is the Allah of Arab Christians. This is a oft-repeated claim by those who want to say that Jews, Christians, and (later) Muslims are all worshiping the same God. The implication seems to be that if they could all just realize this fact, then centuries of conflict could come to an end.
The key, in my opinion, is not to get caught up in how the name Allah happens to be used (e.g., a valid name for Yahweh in the Arabic Bible). Instead, we need to compare the attributes of the Allah of Islam vs. the Allah of Arabic Christians. When we do, we find immediately that the Allah of Islam cannot be the Allah of Arabic Christianity because the Allah of Islam has no Son - Islam completely denies and rejects the concept of the Trinity (and many other aspects of the True God). Therefore, what a Muslim means by Allah is fundamentally different than what we mean by God or Jehovah (or an Arabic Christian means by Allah).
This is much like interacting with cults who tend to use the same language to describe different concepts and identities. The Allah of Islam is no more an accurate description of the True God than the Jesus Christ of Mormonism is Our Divine Savior.  In both instances, the same words or names are used, but entirely different meanings are poured into them. Yet, communication involves both syntax (words) and semantics (meaning). It doesn't follow that just because the words are the same they mean the same thing. Ultimately, it is meaning which is determinative for true communication.
A former Muslim, now a Christian, observes:
May I state for the record, Allah is not the Arabic term for "God." Allah is an idol. In all our debates in universities and colleges, my brother and I have never found one Muslim ulema who believes that Allah of the Qur'an and the God of the Bible are the same God. Never. If monotheism is the sole measure of truth in this case, if Allah is the same god as the true and living God, then Elijah owes the prophets of Baal (also monotheistic) an apology. So why use the term? I asked a Christian Arab why he continues to use the term Allah when he prays, and he whispered to me, "I cannot bring myself to use the Hebrew names, you know?" Yes, I know. Sadly, I know. So the argument that Allah of Islam is the same God as the Allah of Christian Arabs (and the Jehovah or Yahweh of English Christians) is a red-herring. The real issue is whether Allah describes the same entity. Since the Allah of Islam has no Son whereas the Allah of Arab Christianity has both a divine Son and a Holy Spirit (the Trinity), the words do not describe the same concept or person. To a Muslim, Allah describes his concept of God. To a Christian Arab, Allah also describes his concept of God. But the two concepts are radically different so the superficial agreement in terms is of little consequence.
 Mormonism, like many other cults, denies the deity of Jesus Christ.
 Ergun Caner, "The MBB's Dirty Little Secret," Israel My Glory, November/December 2004, p. 10.