The root ᴹ√ROY “ruddy, red” appeared in The Etymologies of the 1930s with Noldorin variant ᴹ√GROJ and derivatives ᴹQ. roina/N. gruin “ruddy” (Ety/ROY²). The latter seems to be an element in the names N. Dunruin “Red Valley” and N. Ruinnel “Redway” from Lord of the Rings drafts from the 1940s (RS/464; TI/114). These names eventually became S. Nanduhirion “Dimrill Dale” and S. Celebrant “Silverlode” (LotR/283; LotR/341).
A similar root √RUYU “blaze (red)” appeared in 1964 notes on Dalath Dirnen (DD), with derivatives like Q. ruinë “fire, blaze” and Q. ruimen/S. ruist “fireplace, hearth”. In this note Tolkien contrasted Q. ruine “fire, blaze” with nār- “fire as an element”. The note seems to be inspired by a proposed alternate name S. Angruin “Iron Fire” for S. Glaurung; this alternate name was rejected with an “X”, but the rest of the note was allowed to stand. It’s probable the element -ruin is the same one seen in S. Orodruin “Mountain of Fire” (LotR/899), a name that dates back to Lord of the Rings drafts from the 1940s.
The word ruin in turn was connected to the root √RUN “red, glowing” in notes associated with The Shibboleth of Fëanor from 1968, having derivatives Q. runya/S. ruin “fiery red” (PM/365-6 note #61). Thus we tentatively have the conceptual development: 1930s ᴹ√ROY² “ruddy, red” >> 1964 √RUY “blaze (red)” >> 1968 √RUN “red, glowing”.
Neo-Eldarin: For purposes of Neo-Eldarin, I’d stick with 1964 √RUY “blaze (red)” as the version of the root having the largest and must useful set of derivatives.
Derivatives
Q. (apa)ruivë “wild fire, fire as conflagration” ✧ PE17/183
The root ᴹ√ROY “ruddy, red” appeared in The Etymologies of the 1930s with Noldorin variant ᴹ√GROJ and derivatives ᴹQ. roina/N. gruin “ruddy” (Ety/ROY²). The latter seems to be an element in the names N. Dunruin “Red Valley” and N. Ruinnel “Redway” from Lord of the Rings drafts from the 1940s (RS/464; TI/114). These names eventually became S. Nanduhirion “Dimrill Dale” and S. Celebrant “Silverlode” (LotR/283; LotR/341).
A similar root √RUYU “blaze (red)” appeared in 1964 notes on Dalath Dirnen (DD), with derivatives like Q. ruinë “fire, blaze” and Q. ruimen/S. ruist “fireplace, hearth”. In this note Tolkien contrasted Q. ruine “fire, blaze” with nār- “fire as an element”. The note seems to be inspired by a proposed alternate name S. Angruin “Iron Fire” for S. Glaurung; this alternate name was rejected with an “X”, but the rest of the note was allowed to stand. It’s probable the element -ruin is the same one seen in S. Orodruin “Mountain of Fire” (LotR/899), a name that dates back to Lord of the Rings drafts from the 1940s.
The word ruin in turn was connected to the root √RUN “red, glowing” in notes associated with The Shibboleth of Fëanor from 1968, having derivatives Q. runya/S. ruin “fiery red” (PM/365-6 note #61). Thus we tentatively have the conceptual development: 1930s ᴹ√ROY² “ruddy, red” >> 1964 √RUY “blaze (red)” >> 1968 √RUN “red, glowing”.
Neo-Eldarin: For purposes of Neo-Eldarin, I’d stick with 1964 √RUY “blaze (red)” as the version of the root having the largest and must useful set of derivatives.