Albert Barnes Commentary Daniel 2:26

"The king answered and said to Daniel, whose name was Belteshazzar, Art thou able to make known unto me the dream which I have seen, and the interpretation thereof?" — Daniel 2:26 (ASV)

The king answered, and said to Daniel, whose name was Belteshazzar - See the notes at (Daniel 1:7). The “king” may have addressed him by this name, and probably did during this interview. This was the name, it would seem, by which he was known in Babylon—a name which implied honor and respectability, as it was conferred on one whom, it was supposed, the principal Babylonian divinity favored.

Art thou able to make known unto me the dream? - One of the first points in the difficulty was to recall “the dream itself,” and hence, this was the first inquiry which the king presented. If he could not recall that, of course the matter was at an end, and the law would be allowed to take its course.