Notice how each verse in Isaiah 21 is linked to the chapter of the 21st book, Ecclesiastes:
6 The wind goeth toward the south, and turneth about unto the north; it whirleth about continually, and the wind returneth again according to his circuits.
1 The burden of the desert of the sea. As whirlwinds in the south pass through; so it cometh from the desert, from a terrible land.Ecclesiastes 2
17 Therefore I hated life; because the work that is wrought under the sun is grievous unto me: for all is vanity and vexation of spirit.
2 A grievous vision is declared unto me; the treacherous dealer dealeth treacherously, and the spoiler spoileth. Go up, O Elam: besiege, O Media; all the sighing thereof have I made to cease.Ecclesiastes 3
10 I have seen the travail, which God hath given to the sons of men to be exercised in it.
3 Therefore are my loins filled with pain: pangs have taken hold upon me, as the pangs of a woman that travaileth: I was bowed down at the hearing of it; I was dismayed at the seeing of it.