Message to Aragorn
Where now are the Dúnedain, Elessar, Elessar?
Why do thy kinsfolk wander afar?
Near is the hour when the lost should come forth,
And the Grey Company ride from the North.
But dark is the path appointed for thee:
The Dead watch the road that leads to the Sea.
Message to Legolas
Legolas Greenleaf long under tree
In joy thou hast lived. Beware of the Sea!
If thou hearest the cry of the gull on the shore,
Thy heart shall then rest in the forest no more.
“Greenleaf” as an epithet is simply a translation of “Legolas” into the Mannish tongue. The Sindarin name is formed by  laeg ,  leg , (green), and “golas” (a collection of leaves, foliage) . 
 Legolas was a Silvan Elf, son of Lord Thranduil of the Woodland Realm under Mirkwood, so he was literally “long under tree” for most of his life (or at least as a part of his identity as a Silvan Elf). 
 Interestingly, the woods known as Mirkwood were renamed  “Wood of Greenleaves”  ( Eryn Lasgalen  in Sindarin) by Elrond and Thranduil after the  shadow  vanished after Sauron’s defeat.