A noun in The Etymologies of the 1930s glossed “ground, floor” derived from the root ᴹ√TALAM “floor, base, ground” (Ety/TAL). It has a plural form teleif in keeping with Noldorin plural patterns; in Sindarin its plural would be ^telaif. Its Quenya cognate was ᴹQ. talan, and in later writings this pair became Q. talan/S. talan “flat space, platform” < √TALAM (PE17/52), both demonstrating the ancient sound change whereby [[p|final [m] became [n]]] (VT47/24).
Neo-Eldarin: In later writings, S. talan was used mainly to refer to an elevated platform or floor, such as the flets of Lothlórien. As such, I think it is worth retaining talaf to refer both to the ground floor as well as the ground itself, perhaps from a variant ancient form ✱talamē.
An unglossed adjectival form of N. celeb “silver” appearing in The Etymologies of the 1930s under the root ᴹ√KYELEP “silver” (Ety/KYELEP). Tolkien equated this adjective to ᴹQ. telpina, which in an earlier version of the entry was glossed “of silver”, so that is the likeliest meaning of celevon. The actual cognate seems to be ᴹQ. telemna, and the likely primitive form was ✱kyelepnā, with the sound changes pn > bn and ultimately to vn, after which the now-final vn became syllabic to produce -von. Tolkien gave an archaic form celefn where fn represented [vn] as was generally the case in Noldorin of the 1930s.
Neo-Sindarin: For purposes of Neo-Sindarin, I would use celevon as an adjective meaning “[made] of silver”, as opposed to celebrin “like silver (in hue or worth)” (PE17/42).
Conceptual Development: Early adjectives of similar meaning included G. celeptha “silvern” from the Gnomish Lexicon of the 1910s (GL/25) and ᴱN. celaith “of silver” from Early Noldorin Word-lists (PE13/140). Both words were probably derived from ✱kelepta, with the 1920s form reflecting the Early Noldorin vocalization of p to i before spirants.