S. Lhûn loc. “Deep of Water”
The Sindarin name of the river Lune (LotR/1134).
Conceptual Development: When this name first appeared in Lord of the Rings drafts from the 1940s, N. Lhûn was translated “Blue River” (TI/124), clearly based on the Noldorin word for “blue”: lhûn (Ety/LUG²). Tolkien later changed the Sindarin word for “blue” to luin, so this derivation no longer worked. At one point he even considered renaming the river to Sîr Luin, but decided against it since Lhûn already appeared on the published maps of The Lord of the Rings (VT48/28).
In his “Words, Phrases and Passages from The Lord of the Rings” from the 1950s-60s, Tolkien considered a variety of derivations for this name (PE17/136-7), ultimately connecting it to the root √(S)LOW “flow freely (fully)” from which (h)lô “flood” was derived, as well as Q. lóne “(deep) pool”. He translated the name as “deep of water”, saying that the name originally applied to the gulf rather than the river. Later Tolkien invented another derivation, from the Dwarvish words sulûn/salôn “fall, descend swiftly” (VT48/24).
A fuller discussion of these developments can be found in Patrick Wynne’s article “The Problem of Lhûn” (VT48/26-29).
References ✧ LotRI/Lune; PE17/136-137; RC/773; SI; UTI; VT48/24, 27-28