The Sindarin word for “willow”, derived from the same root √TATHAR as its Quenya cognate tasarë (SA/tathar; PE17/81). Its adjectival form tathren “of willow(s)” is an element in the name Nan-tathren “Land of Willows” (S/120).
Conceptual Development: The earliest form of this word was G. tathrin “willow” in the Gnomish Lexicon of the 1910s (GL/69), cognate to ᴱQ. tasarin derived from the early root ᴱ√TASA (QL/53). This was an element in the early names G. Nan Tathrin and G. Dor-tathrin “Land of Willows”, but as a noun rather than an adjective. ᴱN. tathrin “willow” reappeared in Early Noldorin Word-lists of the 1920s (PE13/153), but in The Etymologies of the 1930s Tolkien split it into two words: noun N. tathor “willow” and adjective N. tathren “of willow” under the root ᴹ√TATHAR (Ety/TATHAR).
In notes on Words, Phrases and Passages from the Lord of the Rings from the late 1950s or early 1960s, Tolkien revisited the noun, first having [deleted] S. taur or taor derived from √TASĀR, which he revised to S. tathar derived from √TAÞAR, as noted above (PE17/81). The adjectival form S. tathren continued to appear in Silmarillion drafts of the 1950s and 60s as well (WJ/80).
n.Bot. #willow. >> taor, taur