This was the Quenya word for “silver” throughout Tolkien’s life. The word was derived from the root √KYELEP, which became †tyelpë in Quenya and S. celeb in Sindarin. However, the Quenya form of the word was influenced by Telerin telpë “because the Teleri in their lands, to the north of the Noldor, found a great wealth of silver, and became the chief silversmiths among the Eldar” (Let/426). The archaic Quenya form †tyelpë was retained for the name of the palatal series of tengwar consonants, the tyelpetéma (LotR/1120), but in ordinary use (and most names) the forms telpë or telep- (in compounds) were used.
Conceptual Development: The Qenya Lexicon of the 1910s had ᴱQ. telpe based on the early root ᴱ√TELEPE, but its Gnomish cognate was G. celeb (QL/91). Tolkien did not explain this difference in these early documents from the 1910s. In Early Noldorin Word-lists of the 1920s he had ᴱQ. telqe and ᴱN. celeb “silver” derived from primitive ᴱ✶kelekwé, explaining initial t in the Qenya form as the result of dissimilation away the kw (PE13/140).
In The Etymologies of the 1930s Tolkien introduced a root ᴹ√KYELEP “silver” as an alternate to ᴹ√TELEP, with derivatives ᴹQ. telpe or tyelpe, N. celeb and ᴹT. telpe (Ety/KYELEP). He then said “Q telpe may be Telerin form (Teleri specially fond of silver, as Lindar of gold), in which case all forms may refer to KYELEP”. It seems that he stuck with this idea thereafter and abandoned ᴹ√TELEP.
Note that in the Early Qenya Grammar of the 1920s Tolkien used ᴱQ. telpe for “money” (PE14/54), and I would give telpë this meaning for purposes of Neo-Quenya as well, much like the French word argent means both “silver” and “money”.
tyelpë noun "silver" (KYELEP/TELEP), etymology also in Letters:426 and UT:266. Tyelpë is the true Quenya descendant of primitive ¤kyelepē, but the Telerin form telpë was more common, "for the Teleri prized silver above gold, and their skill as silversmiths was esteemed even by the Noldor" (UT:266). In the Etymologies, tyelpë is also the name of Tengwa #1 with overposed dots, this symbol having the value ty (VT45:25). Cf. tyelpetéma as the name of the entire palatal series of the Tengwar system.