Indeed, there are theories that Islam is an offshoot of Christianity (like Mormonism), in its case an offshoot of Torah-observant Syriac Christianity (possibly the oldest Christian sect, closer to the original sect of Peter than any other: the Nazorians, known to occupy the region between Palestine and Mesopotamia). That would pull along with it all the esoteric theology developed by that sect. And that could thus preserve a pre-Christian Jewish ideology about the angel Israel being Michael and thus in fact the Messiah (and therefore, the Christians then averred, Jesus).

However we cannot prove this on extant evidence because Arabic countries simply did not preserve many records and were rampant with post-hoc editing and doctoring what records they had. This is why we need to verify this existed via Jewish sources. The existence of Islamic sources echoing something similar can then be brought in as supporting evidence (by cladistic logic: the best explanation of how we’d see the same basic idea in three different religions, Judaism, Christianity, and Islam, is if it dates back to their Jewish origins).

I’m curious if the early Christians also could have taken it as an angelic name

Yes. There is some evidence of that. It’s convoluted, but exists. I have a colleague working on a book relating to questions like that.

The gist is that there are obscure references to Israel being one of the names of the angel of Israel (Israel is after all an angelic name: Isra-El, just like Immanu-El and Micha-El etc.), and there are separate obscure references to the angel of Israel being in fact (also named) Michael, and there are separate obscure references to Jesus being (secretly) the angel Michael. So walk that chain of evidence back and you get “Jesus is the angel Israel.” It’s just a convoluted chain and of obscure evidence, so it’s not a slam dunk.

On Jesus as Michael there are already good studies. See my article Was Jesus-Is-Michael an Early Christian Mystery Teaching? (which also shows this may have already been a messianic expectation when Christianity began, that the messiah would secretly be the angel Michael: I note in OHJ that this is strongly implied by Daniel 9 and 12). The book by Hannah that that summarizes discusses the chain of evidence I just mentioned (pp. 88ff. includes what you catch from Philo for example; and there is more than he mentions, but it’s in more difficult sources to date and place).

The reason Justin is not great evidence is that (a) Christian authors of that period are notoriously dishonest and poorly informed (the worst combination) and (b) what they report may be new and peculiar Christian ideas and not anything that goes back to the first century of the religion or Judaism. So it’s hard to make anything out of that. That later anti-Jewish Christians decided that Jesus would replace Israel and invented stories and tales and exegesis to get that result is too self-interested to trust as accurate information relevant to the origin of the religion.

Sources like Philo (and the Talmud and other Judaica) are more valuable because they are less likely to have that kind of explanation (it’s not impossible, but is unlikely).

-:-

Finally: the real lynchpin is the Metatron, not Israel. Every appearance and communication with God in the OT (including the wrestling match and burning bush, and every word spoken by every prophet, unless otherwise attributed), by the time Christianity began, was being credited to a single angel called the Metatron. That may be an office rather than a name, so different angels may have had the assignment. But some sources suggest it was always or usually Michael. That it was then also (secretly) Jesus follows per Hannah.

There is also the Islamic archangel Israfel (Israfil in arabic) who is said to be the oldest of the archangels and mediates between the archangels and God, he is also the one who will blow his trumpet to signify the end (compare with 1 Thessalonians 4:16). In sufi tradition it is also said that the Qutb (basically the ideal man) has a heart that resembles Israfil (similar to Jesus being the moral ideal in both christianity and Islam). To be fair I’m mostly speculating here, some scholars have tried to associate him with Raphael, but there doesn’t seem to be any wide-spread agreement.

But the idea that Jesus is a stand-in for Israel (as the New Israel) is mainstream

In an abstract sense this is clear from the new testament alone, but I’m curious if the early Christians also could have taken it as an angelic name, since, well, it is an angelic name.

The prayer of Joseph seems to confirm there were Jews who believed the first-born archangel is named Israel, and if you squint at what Philo is saying in OCT 146-148, he seems to be saying the same. What really does it for me though is Justin’s comment in chapter 125 in Trypho.

He has a different idea of what happened when Jacob was struggling with the angel than does the author of the prayer, but he outright states that the pre-incarnate Christ was called Israel. Justin is also early and educated enough to have had access to at least some secret teachings that were later forgotten or deemed heretical.

I don’t know the merits of any of that.

But the idea that Jesus is a stand-in for Israel (as the New Israel) is mainstream (Google Scholar returns hundreds of studies on the phrase “Jesus is Israel” and that won’t even be a complete list).

As is also the fact that he is a stand-in for Isaac (reversing the Abraham story, per Hebrews 9) and Moses (as the new Founder and Lawgiver) and Elijah and Elisha (the entire Elijah-Elisha sequence in Luke, but already begun in Mark) and Jesus ben Jehozadak and Jesus ben Ananias and Melchizedek, and even the Rock that provided water to Moses (1 Cor 10). Plus the angel Michael. That’s just the Jewish metaphors he completes. He also stands in for Dionysus, Odysseus, Osiris, and Romulus.

There is a lot of this kind of crazy theorizing in the Dead Sea Scrolls. It was a typical way to think about the coming Messiah. The Christians just picked up and continued the same methods and ideas.

There’s an obscure 1st century Jewish text called the prayer of Joseph which only survives in fragments, the longest of which comes from Origen’s commentary on the gospel of John, here’s the passage:

Jacob, who speak to you, and Israel, I am an angel of God, a ruling spirit, and Abraham and Isaac were created before every work of God; and I am Jacob, called Jacob by men, but my name is Israel, called Israel by God, a man seeing God, because I am the first-born of every creature which God caused to live. When I was coming from Mesopotamia of Syria, Uriel, the angel of God, came forth, and said, I have come down to the earth and made my dwelling among men, and I am called Jacob by name. He was angry with me and fought with me and wrestled against me, saying that his name and the name of Him who is before every angel should be before my name. And I told him his name and how great he was among the sons of God; Are you not Uriel my eighth, and I am Israel and archangel of the power of the Lord and a chief captain among the sons of God? Am not I Israel, the first minister in the sight of God, and I invoked my God by the inextinguishable name?

Commentary on the Gospel of John 2.25
Throughout the old testament Israel is frequently referred to as the first-born of God, and many of the prophecies the NT authors claim are about Jesus actually make a lot more sense in this light. Take Hosea 11:1, quoted in Matthew 2:15 as being about Jesus:

When Israel was a child, I loved him, and out of Egypt I called my son

Then there are the servant songs in Deutero-Isaiah, which is taken as a prophecy about Jesus despite the text identifying the servant as Israel (In-fact Justin Martyr makes this connection, see bellow). Compare also the statement that Abraham and Isaac (presumably also angelic beings in this text) existed before creation with John 8:58

Now let’s turn to Philo’s Logos: In “on the confusion of tongues Philo says the following:

But if there be any as yet unfit to be called a Son of God, let him press to take his place under God’s First-born, the Word, who holds the eldership among the angels, their ruler as it were. And many names are his, for he is called, “the Beginning,” and the Name of God, and His Word, and the Man after His image, and “he that sees,” that is Israel.

And therefore I was moved a few pages above to praise the virtues of those who say that “We are all sons of one man” (Gen. 42:11). For if we have not yet become fit to be thought sons of God yet we may be sons of His invisible image, the most holy Word. For the Word is the eldest-born image of God.

And often indeed in the law-book we find another phrase, “sons of Israel,” hearers, that is, sons of him that sees

OCT 146-148

The earlier passage being passage 41

And therefore when I hear those who say “We are all sons of one man, we are peaceful” (Gen. 42:11), I am filled with admiration for the harmonious concert which their words reveal. “Ah! my friends,” I would say, “how should you not hate war and love peace—you who have enrolled yourselves as children of one and the same Father, who is not mortal but immortal—God’s Man, who being the Word of the Eternal must needs himself be imperishable?”

Now from the above considerations alone I think we’d have sufficient reason to suspect Jesus’ angelic name is Israel, but we don’t even need to speculate since we have Justin Martyr telling us as much in his Dialogue with Trypho,

Again in Isaiah, if you have ears to hear it, God, speaking of Christ in parable, calls Him Jacob and Israel. He speaks thus: ‘Jacob is my servant, I will uphold Him; Israel is my elect, I will put my Spirit upon Him, and He shall bring forth judgment to the Gentiles

Ch 123

And

Accordingly the name Israel signifies this, A man who overcomes power; for Isra is a man overcoming, and El is power. And that Christ would act so when He became man was foretold by the mystery of Jacob’s wrestling with Him who appeared to him, in that He ministered to the will of the Father, yet nevertheless is God, in that He is the first-begotten of all creatures […] But Israel was His name from the beginning, to which He altered the name of the blessed Jacob when He blessed him with His own name, proclaiming thereby that all who through Him have fled for refuge to the Father, constitute the blessed Israel.

Ch 125

And

But if you knew, Trypho, who He is that is called at one time the Angel of great counsel, and a Man by Ezekiel, and like the Son of man by Daniel, and a Child by Isaiah, and Christ and God to be worshiped by David, and Christ and a Stone by many, and Wisdom by Solomon, and Joseph and Judah and a Star by Moses, and the East by Zechariah, and the Suffering One and Jacob and Israel by Isaiah again, and a Rod, and Flower, and Corner-Stone, and Son of God, you would not have blasphemed Him who has now come

Ch 126

And

when Scripture says, ‘I am the Lord God, the Holy One of Israel, who have made known Israel your King,’ Isaiah 43:15 will you not understand that truly Christ is the everlasting King? For you are aware that Jacob the son of Isaac was never a king. And therefore Scripture again, explaining to us, says what king is meant by Jacob and Israel: ‘Jacob is my Servant, I will uphold Him; and Israel is my Elect, my soul shall receive Him. I have given Him my Spirit; and He shall bring forth judgment to the Gentiles. He shall not cry, and His voice shall not be heard without. The bruised reed He shall not break, and the smoking flax He shall not quench, until He shall bring forth judgment to victory. He shall shine, and shall not be broken, until He set judgment on the earth. And in His name shall the Gentiles trust.’ Isaiah 42:1-4 Then is it Jacob the patriarch in whom the Gentiles and yourselves shall trust? Or is it not Christ? As, therefore, Christ is the Israel and the Jacob, even so we, who have been quarried out from the bowels of Christ, are the true Israelitic race

Ch 135

Lots and lots of other examples in Justin, but I think this gets the point across.

I haven’t seen any scholars make this connection but I think it might be worth looking further into, although I’m merely a layman.

Note I reference the ahistoricity suspicions in the peer reviewed literature for Buddhism and Confucianism in OPH as well (only in passing, p. 377, but with a bibliography).

I may post a separate comment on why studying Mormonism is important & the 2 Davids’ books on the topic. I don’t think I’ve ever posted a blog comment but am a Patreon supporter.

Hard to say. I’d put the hypotheses in this order (roughly):

42% it was forged in the 18th/19th century.
38% Morton forged it.
15% it was forged in the Middle Ages.
> 4% it is authentic but Clement was duped by a forged text of Mark.
< 1% it is all authentic.