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.
An earlier name of Celebrant in Lord of the Rings drafts from the 1940s (TI/241), apparently celeb “silver” or celebren “of silver”, combined with rath “course, river-bed”.