The speaker's talk about the wind "passing through" or "passing by" gives us a sense of the natural sort of way that the wind exists in the poem, and in life, without any frills or big takeaway meanings. The wind is just doing its thing and so are the trees.
- Lines 3-4: It's as simple as "the wind is passing through." No need to have any super ornate language invoking the gods of wind and such. The wind exists simply and naturally as it passes through and makes the leaves tremble.
- Lines 7-8: It's just as simple when the trees "bow down their heads" to allow to wind to pass by. The trees and the wind have a kind of mutual understanding and respect that doesn't require any fancy language or explanations.