Jeremiah 25:26 - Matthew Poole's English Annotations on the Holy Bible

All the kings of the north, far and near; all under the government of the Chaldeans, or (as others) all those princes that have dominions between the north and east. All the kingdoms of the world, which are upon the face of the earth; that is, in those parts of the world which were at that time known, with whom there was ordinary commerce. And the king of Sheshach shall drink after them; and the king of Babylon, who was last of all to drink of this cup of the Lord's fury. That he is here meant is plain from Jeremiah 51:41, where Sheshach is thus interpreted. But why Babylon is called Sheshach is a harder question, and not easily resolved. Those who think the prophet gives Babylon here another name to avoid an odium fresh the king of Babylon, at this time their enemy, neither consider the usual courage of this prophet, nor that he speaks plainly enough, Jeremiah 51:41, where he mentioneth both Babylon and Sheshach, and expoundeth the latter by the former. It is thought that Babylon is called Sheshach from the name of an idol called Shach which they worshipped, to whose honour they yearly kept a festival for five days together, which they called Shace, and they say that during this festival Cyrus took Babylon. But these are all uncertain guesses; it is enough for us to know that by the king of Sheshach is meant the king of Babel, as the prophet expounds himself, Jeremiah 51:41.