Out of the north. There was a peculiar mystery attaching to the north in the Hebrew mind, as, in fact, the word very for "north" in Hebrew (literally, the hidden) indicates. The burnt offering was to be sacrificed on the north side of the altar (Le Jeremiah 1:11), and the four cherubim, in the vision of Ezekiel, are described as coming from the north (Ezekiel 1:4).
The horror with which Babylon was regarded was intensified, apparently, by its northern position (Jeremiah 1:14), and now the "hidden" north again pours forth its swarms of warriors against Babylon herself.
They shall remove, they shall depart; rather, they are fled, they are gone; almost the same clause occurs in Jeremiah 9:10. The prediction is realized as past.