√LAS² root. “listen”
This root did not appear as the basis of “listen” words until The Etymologies of the 1930s, where Tolkien gave ᴹ√LAS² “listen” as opposed to ᴹ√LAS¹ “leaf” (Ety/LAS¹, LAS²). One of its derivatives was N. lhewig “ear” (from fossilized dual lhaw). Tolkien apparently wanted to retain this form in his later writings after deciding that initial l was no longer unvoiced in Sindarin, so he coined a variant s-fortified root √SLAS “ear” from which it could still be derived (PE17/62, PE17/77). The unfortified root √LAS “listen” continued to appear, however (PE17/46; PE19/101), as indicated by imperative S. lasto “listen” (LotR/307). Tolkien did speculate that the roots √LAS¹ “leaf” and √LAS² “listen” might ultimately be related, probably because of the similarity of the shape of Elvish ears and the leaves of trees:
lasse “leaf” (S las); pl. lassi (S lais). It is only applied to certain kinds of leaves, especially those of trees, and would not e.g. be used of leaf of a hyacinth (linque). It is thus possibly related to √LAS “listen”, and S-LAS stem of Elvish words for “ear”: Q hlas, dual hlaru. Sindarin dual lhaw, singular lheweg (PE17/62).
A similar notion appeared in The Etymologies: “Some think this [ᴹ√LAS¹ ‘leaf’] is related to the next [ᴹ√LAS² ‘listen’] and *lassē ‘ear’. The Quendian ears were more pointed and leaf-shaped than [?human]” (Ety/LAS¹).
References ✧ PE17/46, 62, 159; PE19/101
ᴹ√LAS² root. “listen”
Reference ✧ Ety/LAS² ✧ “listen”
?ᴱ√HIÞI root. “*listen”
A hypothetical early root explaining words in the Gnomish Lexicon of the 1910s such as G. hist “listening, attention” and hitha- “listen, hearken, listen to” (GL/49). There are no signs of this root in Tolkien’s later writing.