In the Quran, Muhammad constantly claimed to be continuing in the revelation given to the Biblical authors, given by the very same God. For example:
Surah 3:3
3 He has revealed to you ˹O Prophet˺ the Book in truth, confirming what came before it, as He revealed the Torah and the Gospel
This is how Muhammad attempted to circumvent the fact that all new religions are false, because God has never left mankind without a witness. And, without this historical link, there was no reason to give any weight to Muhammad's claims of prophethood.
However, in the Bible which he claimed to affirm, God's proper name is given, and it is represented by the Hebrew word "יְהֹוָה", transliterated into English in a consonantal form as the letters YHWH. This has historically been rendered in English as "Jehovah", though the more popular modern rendition is "Yahweh":
Exodus 3:13-15 (LSB)
13 Then Moses said to God, "Behold, I am about to come to the sons of Israel, and I will say to them, 'The God of your fathers has sent me to you.' And they will say to me, 'What is His name?' What shall I say to them?"
14 And God said to Moses, "I AM WHO I AM"; and He said, "Thus you shall say to the sons of Israel, 'I AM has sent me to you.'"
15 And God furthermore said to Moses, "Thus you shall say to the sons of Israel, 'Yahweh, the God of your fathers, the God of Abraham, the God of Isaac, and the God of Jacob, has sent me to you.' This is My name forever, and this is My memorial-name from generation to generation.
In the above, God reveals His eternal name to Moses. And, it is not a generic name for "God" in Hebrew, or any language. That would be "Elohim", in Hebrew, "God" in English, and so on. Instead, it is a proper name.
Critically, this name has the historical foundation of being embedded in the names of many people in the Bible, including many prophets.
For example:
Above, even in their English renditions, one can still see "Yah" (יָהּ), or "Jah", a shortened form of "Yahweh" used by God over 40 times in Scripture (Psalm 68:4, Exodus 15:2, Isaiah 12:2, etc.), and the basis for words like "Hallelujah" (Psalm 104:35 [הַלְלוּיָהּ], Revelation 19:1-6 [ἀλληλούΐα], etc.), in many of these names.
And, the last name in the list above, "Joshua", when transliterated into Greek, is Iēsous. That Greek name brought into English is Jesus. So, the name "Jesus" contains this name of God, and means "Yahweh saves". The angel that gives His name to Joseph references this in the New Testament:
Matthew 1:21
21 And she shall bring forth a son, and thou shalt call his name JESUS: for he shall save his people from their sins.
There are also other people in the New Testament with names derived from Yahweh, such as "John", derived from יְהוֹחָנָן, meaning "Yahweh is gracious", or "Yahweh is merciful". Similar to Jesus, this name was given to John the Baptist directly by God (Luke 1:13). However, Jesus is of course the most significant example, both in Christianity and Islam.
Therefore, the name of God in Christianity is consistent in both the Old and New Testament, in a prominent, obvious way. It has a clear, certain historical testimony.
In spite of Muhammad's claim to be continuing in the line of the Biblical prophets, the name Yahweh is never used for God anywhere in the Quran, or the Hadith, by Muhammad. Instead, he exclusively used the Arabic word Allah (ﷲ), which means "The God", as the proper name of God. In this way, it is generic in the same sense that Elohim (Hebrew), or Theós (Greek) is generic.
In addition to the proper name "Allah", Muhammad gave 99 other "names" of Allah, which are more like titles, or descriptions of attributes. Some Muslims have tried to find in one of these names a name that means the same thing Yahweh means, essentially, "I am who I am". But, this is not what we are looking for. The main name of God, being relegated to just one name out of 99 names, and supplanted altogether with an entirely different term, would still demonstrate that Muhammad was ignorant of the significance of the name. And, considering that the name's literal meaning describes, in essence, a necessary aspect of all Theistic concepts of God, it is not surprising that it would be encompassed by a person enumerating 99 different ways of describing God, once again, despite being entirely ignorant of the special significance given to that name explicitly.
In the Old Testament, the divine name of God is revealed, and used thousands of times thereafter. In the New Testament, new characters are introduced, who were both named directly by God, and have that divine name embedded in their name. Therefore, the name is referenced hundreds of times in the New Testament, too, in new, and meaningful ways. In contrast, it is utterly unknown in Islam, except on accident, because Muhammad usurped characters from Christianity.