the Most High: God named as the one who stands above every other power, throne, and kingdom
In Aramaic this word simply means "high" or "upper," and in the Bible it does only one job: it names God. All ten of its appearances sit in the Aramaic chapters of Daniel, and not one of them describes a high wall or an upper floor. Every time, the one who is highest is God.
It turns up in two shapes. Four times it stands beside the ordinary Aramaic word for God (אֱלָה), giving "the Most High God": the God being spoken of is marked out as the one at the top. Six times it stands on its own and works like a name, so that "the Most High" is simply who God is, as in the refrain of Daniel 4 that the Most High rules over human kingdoms and hands them to whomever he wishes.
Part of what makes the word striking is who says it. The speakers are mostly outsiders: Nebuchadnezzar reporting what happened to him, the heavenly watchers issuing their decree, Daniel explaining to Belshazzar how his father learned the lesson. "The Most High" is the name for Israel's God that a Babylonian court can pronounce, a title about rank rather than about covenant, and Daniel uses it to press the point every empire needs to hear: the throne above all thrones is not in Babylon.
Daniel 7 carries the title into a courtroom of a different kind. There a beastly king "speaks words against the Most High," and a few words later the verse switches to a closely related Aramaic word (עֶלְיוֹן) for the holy ones who belong to him. The offense is not just political rebellion; it is talking back to the one who is over everything.