The word celeb was the word for “silver” in Sindarin and its conceptual precursors throughout Tolkien’s life.
Conceptual Development: G. celeb “silver” appeared all the way back to the Gnomish Lexicon of the 1910s, where it was related to the early root ᴱ√TELEPE of the same meaning (GL/25; QL/91). In Early Noldorin Word-lists of the 1920s ᴱN. celeb was derived instead from ᴱ✶kelekwé with the sound change of primitive kw to p and later to b (PE13/140), though in that same document he considered (but rejected) ᴱ✶t’lépe > ᴱN. tlub “silver” (PE13/154). In The Etymologies of the 1930s Tolkien introduced a new root ᴹ√KYELEP “silver” to be the basis of N. celeb, with the sound change whereby intial ky became k (c) (Ety/KYELEP). This sound change continued to be a feature of Sindarin of the 1950s and 60s, and Tolkien retained this derivation going forward.
A stream flowing through Dimrill Dale translated “Silverlode” (LotR/341) or “Silver-course” (RC/262). It is itself a translation of Kh. Kibil-nâla of the same meaning (PE17/35, TI/174). This name is a combination of celeb “silver” and rant “course” (RC/775).
Conceptual Development: In Lord of the Rings drafts from the 1940s, this river was first named “Red Way”: N. Crandir along with other variations (RS/432-3). Tolkien changed the name to N. Celebrin “✱Silver” (RS/434) and later N. Celeb(rind)rath “Silverlode” (TI/241) before settling on N. Celebrant (TI/235). The final name also appeared in The Etymologies as a river-name, without translation (Ety/RAT).