the east wind: the hot, dry, violent wind that blows in off the desert and withers or destroys whatever it touches
In the land of the Bible the wind from the east comes off the desert, and it is the cruelest wind there is: scorching, parched, and strong enough to flatten crops, dry up springs, and break ships. So when writers reach for this word they are almost never describing a gentle breeze. They mean the blast that shrivels grain, burns the green plant brown, and leaves the land gasping.
Because it is so destructive, the east wind became a ready picture of ruin sent by God. Again and again it is the tool in his hand: it drives the locusts into Egypt, it parts the sea, it shatters the proud ships of Tarshish, it dries up the fountain of a guilty nation. The word carries that double weight at once, a real weather event and a sign of judgment.
It also became a figure of speech for anything empty or fleeting. A foolish man fills himself with the east wind, that is, with hot air that nourishes nothing. Israel chases the east wind all day long, pursuing what cannot be caught. The same harsh, futile force that ruins a harvest stands for words and pursuits that come to nothing.