A Noldorin name for Ulmo appearing only in The Etymologies from the 1930s (Ety/NU), apparently a masculinized form of nûr “deep” and with the suffix -on.
Noldorin
ul-
prefix. *ugly
eil-
verb. to rain
lhorn
noun. quiet water
lhorn
noun. anchorage, harbour
nen
noun. water (used of a lake, pool or lesser river)
nen
noun. waterland
nen
noun. water
núron
masculine name. Ulmo
uiar
masculine name. Ulmo
Noldorin name of ᴹQ. Ulmo from The Etymologies from the 1930s (Ety/WAY), also appearing as Guiar (Ety/ULU), derived from the primitive form ᴹ✶Wāyārō.
Conceptual Development: In the Gnomish Lexicon from the 1910s, his name was given as G. Gulma (GL/18, 43), but appears as Ulm or Ulum in “Official Name List” for the Lost Tales (PE13/101). In the Lays of Beleriand from the 1920s, his name was first given as Gulma but was revised to ᴱN. Ylmir (LB/93), a form that reappeared in the earliest Silmarillion drafts (SM/13).
An impersonal verb appearing as N. eil “it is raining” in The Etymologies of the 1930s derived from primitive ᴹ✶ulyā- (> œil > eil) under the root ᴹ√ULU “pour, flow” (Ety/ULU; EtyAC/ULU). This verb is abnormal in that its final a disappeared rather than surviving as it usually did for derived verbs, giving eil rather than ✱elia-, ✱eilia- or ✱eila-. However, as an impersonal verb there would never be any pronominal suffix to help preserve the final a by analogy, which explains the vowel loss.
Conceptual Development: The verb for “rain” in the Gnomish Lexicon of the 1910s was G. ubra-, probably related to G. ub “wet, moist, damp” (GL/74).
Neo-Sindarin: In Sindarin, the likely development of primitive ✶ulyā would be to ✱oly(a) > ᴺS. uil “it rains”; I believe this form was first suggested by Helge Fauskanger in his Parviphith Edhellen wordlist. Compare ᴺS. uil to: S. ruin “fiery red” < (perhaps) ✱runyā and S. fuir “north” < (perhaps) ✱phoryā, and see the entry on how [[s|[œi] became [ui] or [y]]] for further discussion. Any inflected forms would probably restore the stem, such as (hypothetical) intransitive past and future forms ✱eilias “it rained” and ✱eiliatha “it will rain”).