This root first appeared as unglossed ᴱ√RINI in the Qenya Lexicon of the 1910s with derivatives like ᴱQ. rin (rind-) “year, circle” and ᴱQ. rinko “disc, orb, circle” (QL/80). It also had derivatives in the contemporaneous Gnomish Lexicon such as G. rin- “revolve, return, come back; do again” and G. rinc “circular; disc, rondure” (GL/65), but also strengthened forms like G. †drinn “ring, disc” and G. drintha- “to turn (tr.), twist” (GL/30). The root reappeared in The Etymologies of the 1930s with derivatives like ᴹQ. rinda/N. rhenn “circular” and ᴹQ. rinde/N. rhinn “circle” (Ety/RIN).
Middle Primitive Elvish
lin
root. pool
lin
root. sing
li
root. many; large people
ailin
noun. pool, lake
angwa
root. snake
nī
noun. woman
nī̆s
noun. woman
rin
root. *circle
wis
root. air
The root √ANGWA “snake” with variant √ANGU appeared in The Etymologies of the 1930s as the basis for the words ᴹQ. ango “snake” (Ety/ANGWA) and angulóke “dragon” (Ety/LOK). The Noldorin equivalent am- seems to have survived only as a prefix (Ety/ANGWA), and is a good example of how [[on|[ŋgw] > [mb]]] in that language. There are a variety of other words for “snake” in Tolkien’s later writings, so whether this root remained valid is unclear.