A root appearing as √(N)DIP/B “bending and drooping” in notes probably from around 1959 given as an influence on S. nimp “pale, pallid”, and as a variant of √(N)DUB of similar meaning (PE17/168). Its Quenya derivatives Q. nimpa “drooping” and Q. limpa “frail” indicate both the strengthened and unstrengthened forms were in use. Based on the derived forms, probably √(N)DIP meant “droop” vs. √(N)DUB = “bend”.
Primitive elvish
(n)dub
root. bending and drooping, bending, drooping
(n)dip
root. bending and drooping, drooping, bending
kait-a
verb. lie, be on the ground
kay
root. lie, lie, [ᴹ√] lie down; [ᴱ√] rest, dwell
Tolkien used this root for “lie (down)” for most of his life. It appeared as ᴱ√KAYA “lie, rest; dwell” in the Qenya Lexicon of the 1910s (QL/46), but in that document there was another root ᴱ√KAMA “lie down”, with the derivative ᴱQ. kama- “to lie down” (QL/44). There is no sign of ᴱ√KAMA¹ being used this way after the 1910s, and in the 1920s Early Qenya Grammar, the verb for “lie down” was kaita- (PE14/58), which in the Qenya Lexicon of the 1910s had the transitive sense “to place” (QL/44).
The root ᴹ√KAY “lie down” reappeared in The Etymologies of the 1930s (Ety/KAY), and it appeared again in the Quenya Verbal System (QVS) from 1948 as the basis for the verb ᴹQ. kaita- “to lie (down)” (PE22/126). The root and associated Quenya verb continued to appear in Tolkien’s later writings all the way up through the late 1960s, always with the sense “lie” (PE17/72; PE22/156).
A root appearing as √(N)DUP/B “bending and drooping” in notes probably from around 1959 given as the basis for Q. lúva “bend, bow, curve” and Q. numba “bent, humped”, so most likely meaning “bend” as opposed to √(N)DIP/B = “droop”, another root appearing in the same note; the pair was glossed “bending and drooping” (PE17/168). In another set of notes written between the first and second edition of The Lord of the Rings, Q. lúva “bow, bight” was derived from √LUB “bend” (PE17/122). Yet another probably related primitive form is ✶luʒu > ✶lū in a discussion of monoconsonantal primitive roots from 1968; one of the derivatives of ✶luʒu was Q. luhta- “to bow” (VT47/35). Of the three, I prefer √(N)DUB as the basis for Q. lúva for purposes of Neo-Eldarin, as it has the greatest set of derivatives and related forms.