Ecclesiastes starts and ends with this verse :

Ecclesiastes 1:1-2 “The words of the Preacher, the son of David, king in Jerusalem. Vanity of vanities, saith the Preacher, vanity of vanities; all is vanity.”
Ecclesiastes 12:8 “Vanity of vanities, saith the preacher; all is vanity.”

The hebrew word for vanity is Hebel H1892 – heḇel, which actually means breath or vapor!! So he could be saying, “it is just all breath and vapor, breath that vaporises..”

Throughout Ecclesiastes some translations keep repeating the words also “it is like trying to catch the wind“, for example Ecclesiastes 2:17. However the word for wind there is Ruach H7307 – rûaḥ, meaning spirit! It also points to the spirit being and acting like the wind, even breath and the mind, or air. And the word for “cathing” the wind, in hebrew is Reut H7469 – rᵊʿûṯ, meaning to strive with or for, longing. So in hebrew it actually says to long in your spirit for something, or striving in the spirit.

So to re-translation or re-word, you could say “it is just all breath and vapor, breath that vaporises while the spirit is longing“

Ecclesiastes ends the book with the Conclusion About Mankind : Ecclesiastes 12:13 “Let us hear the conclusion of the whole matter: Fear YHWH, and keep his commandments: for this is the whole of man (purpose of man)”