A root in The Etymologies of the 1930s glossed “hump”, with Quenya and Noldorin derivatives of the same meaning (Ety/TUMPU). It might be a later iteration of the root ᴱ√KUPU “hump” from the Qenya Lexicon of the 1910s which had derivatives like ᴱQ. kumpo “pile” and ᴱG. cub “hollow” (QL/49; GL/27). Alternately, it could be a later interation of ᴱ√TUMU “swell (with idea of hollowness)” (gloss marked with “?”) from the same document, but the one clear derivative of ᴱ√TUMU was ᴱQ. tumbe “trumpet, large horn” (QL/95), which seems unrelated to 1930s ᴹ√TUMPU.
Middle Primitive Elvish
lum
root. *shadow
lub Reconstructed
root. lump
lub
root. weary
tumpu
root. hump
galan
root. bright
kwentā
noun. tale
lop
root. horse, horse; [ᴱ√] *run (of animals), gallop, lope
This root was the basis for horse words starting with the Qenya Lexicon of the 1910s, where it appeared unglossed as ᴱ√LOPO (QL/56). It was compared to the root ᴱ√LOQO, and these roots include the verbs ᴱQ. lopo- “gallop, run (of animals)” and ᴱQ. loqo- “run (of human beings)”, so I think it is likely those were the meanings of the roots as well (QL/56). In the Qenya Lexicon, ᴱ√LOPO had the derivatives ᴱQ. lōpa “horse or mare” and ᴱQ. lopsi “mare” (QL/56), but elsewhere in that document there was the word ᴱQ. lapatte “rabbit” < ᴱ✶lopatte, so I think that word is related as well, though Tolkien did mark the primitive form with a “?” (QL/51). The probably-related word ᴹQ. lopo “rabbit” appeared in a discussion of nouns from the early 1930s (PE21/31).
In The Etymologies of the 1930s the root ᴹ√LOP was glossed “horse”, and its derivatives ᴹQ. olombo and N. lobor had only that sense (EtyAC/LOP), but horse words were usually derived from ᴹ√ROK from the 1930s and later. The word Q. lopoldi “rabbits” appeared in some 1965 notes on Númenor, so It seems likely √LOP remained valid in some form. Another possibly related late word is S. ✱laba- “hop” as in S. Labadal “Hopafoot” (UT/60).
Neo-Eldarin: For purposes of Neo-Eldarin, I think it is worth retaining ᴹ√LOP with a verbal sense “✱gallop, lope”. In this way, it can remain the basis for rabbit words based on their loping run. The horse words from this root might be specialized for heavier loping horses like destriers, since ᴹQ. rokko was said to refer more specifically to a “swift horse” (EtyAC/ROK).
lug
root. be heavy
A root in The Etymologies of the 1930s glossed “be heavy”, with the derived adjectives ᴹQ. lunga and N. lhong of the same meaning (Ety/LUG¹). Given the appearance of G. lung “heavy; grave, serious” in the Gnomish Lexicon of the 1910s, I think the idea for this root dates back to this period, though the related verb G. luntha- “balance, weigh” indicates the Early-period root may have been ✱ᴱ√LUŊU instead (GL/55). Tolkien’s continued used of Q. lungu- and S. -lung for “heavy” in his later writings indicates its ongoing validity (S/185; PE17/162; VT47/19).
spāna
noun. cloud
ungwē
noun. gloom
wath
root. shade
yen
root. year
A root in The Etymologies of the 1930s glossed “year” with derivatives like ᴹQ. yén/N. în “year” (Ety/YEN). Tolkien’s ongoing use of words like Q. yén and S. ínias “annals” indicate its ongoing validity (LotR/377; MR/200), but in Quenya at least the meaning shifted to that of an “Elvish long year”, equal to 144 solar years (LotR/1107; MR/471; NM/84).
yenrinde
noun. year
A root in The Etymologies of the 1930s glossed “weary”, with derivatives like ᴹQ. lumba and N. lhom of the same meaning (EtyAC/LUB).