To make green or to cover with greenery; to turn something green or cause vegetation to grow.
From en- (to cause to be) + green (from Old English grene, meaning the color green or living vegetation). The prefix transforms the color/adjective into an action.
Medieval poets used 'engreen' to describe spring arriving—as the world transformed from brown and gray back to color, they had this perfect word that captured both the color and the sense of life returning to the landscape.
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