A Quenya name of S. Nan-tathren used by the Ents (LotR/469, SA/tathar), translated “Willow-vale” (RC/384) or “Vale of Willow” (PE17/81). It is a compound of the stem form of tasar(ë) (tasari-) “willow” and the suffix -nan “valley” (SA/tathar, RC/384).
Conceptual Development: The name ᴱQ. Tasarinan appeared in the earliest Lost Tales (LT2/140, 225), though at this early stage its initial element was ᴱQ. tasarin “willow” (QL/89). The name ᴹQ. Tasarinan also appeared in Treebeard’s song in the Lord of the Rings drafts from the 1940s (TI/417).
tasar, tasarë (þ) noun "willow-tree" (TATHAR). In Tasarinan "Willow-valley", Nan-tasarion "Valley of willows" (SA:tathar)