Look at the first stanza. "easy, happy, starry, lordly, barley." The 'y' in barley isn't a suffix, but it's an elegant little echo. "easy" and "happy" are insistent motifs in the poem. Next stanza: "happy, only, mercy, slowly." I love the bittersweetness of "only" and "mercy," where the -y becomes a little filip of innocence under the influence of "happy." Third stanza, laying it on thick: "lovely, lovely, watery, nightly."
All the sun long it was running, it was lovely, the hay
Fields high as the house, the tunes from the chimneys, it was air
And playing, lovely and watery
And fire green as grass.
Now we're mid-poem. Switch! The tone becomes bass-like and sonorous.
And then to awake, and the farm, like a wanderer white
With the dew, come back, the cock on his shoulder: it was all
Shining, it was Adam and maiden,
The sky gathered again
And the sun grew round that very day.
So it must have been after the birth of the simple light
In the first, spinning place, the spellbound horses walking warm
Out of the whinnying green stable
On to the fields of praise.
No '-y' endings here, except for 'very' (and perhaps "whinnying"?) Is that devious or what? Then the next to last stanza: "happy." That's all. But the repetition makes it clear and obvious. Final stanza: "easy, mercy."
Oh as I was young and easy in the mercy of his means,
Time held me green and dying
Though I sang in my chains like the sea.
That final line is well known for its beauty. But marvel for a minute at how that last word, "sea," rolls up like a huge snowball from the white field of all those teeny little words: "easy, happy, starry, watery, lovely."