A noun in The Etymologies of the 1930s glossed “hump” derived from the root ᴹ√TUMPU of the same meaning (Ety/TUMPU). A possible earlier precursor is ᴱN. tuf “lump, knob” from Early Noldorin Word-lists of the 1920s (PE13/154).
Noldorin
tum
noun. (deep) valley
tum
noun. deep valley, under or among hills
tum-halad
place name. Tum-halad
tum dincelon
place name. Dimrill-dale
tump
noun. hump
tumladen
place name. Level Vale
tump
noun. hump
tofn
adjective. lowlying, deep, low
nûr
adjective. deep
doll
adjective. dark, dusky, obscure
dolt
adjective. dark, dusky, obscure
dûr
adjective. dark, sombre
dûr
adjective. dark
imlad
noun. deep valley, narrow valley with steep sides (but a flat habitable bottom)
nanduhiriath
place name. Dimrill-dale
A precursor to S. Nanduhirion “Vale of Dim Streams” appearing in Lord of the Rings drafts from the 1940s (RS/433), apparently ending with the lenited class-plural hiriath of N. sîr “stream”, as suggested by Roman Rausch (EE/1.14).
nanduhirion
place name. Dimrill-dale
nûr
adjective. deep
rhaudh
adjective. hollow, cavernous
rosta-
verb. to hollow out, excavate
tofn
adjective. lowlying, deep, low
Earliest name for S. Nanduhirion appearing in Lord of the Rings drafts from the 1940s (RS/432), apparently starting with N. tum “valley” and ending with Ilk. celon “river”, but the meaning of the middle element is unclear. Roman Rausch suggested it might be related to Ilk. dimb- “sad, gloomy” (EE/1.14).