S. final [vn] sometimes became [von]; [-vn] > [-von]
In Noldorin, there are several examples where a final [-vn] became [-von]:
The last example was deleted and replaced by N. drafn (Ety/DARÁM), and there are a fair number of other examples where final [-vn] was preserved:
It’s not clear whether this sound change could apply to Sindarin; we only have one example of final [-vn], and it was preserved: S. tavn “a thing made by handicraft” (PE17/107). But certainly [-von] is easier for an English speaker to pronounce. Since we only have a single example, it could have been a sporadic change in Sindarin as it was in Noldorin.
It may seem that [-vn] > [-von] is a very specialized change, but aside from [-rn] (which was easily pronounced and remained unchanged), [vn] is the only other surviving combination of a consonant with [n] in Sindarin/Noldorin:
Thus, this change was analogous to the syllabification of final [r], [l] after consonants, producing the same vowel [o]. However, final n-syllabification seems less universal that the l/r-syllabification, happening only sometimes, and sometimes with [-vn] preserved.
Conceptual Developments: There is Gnomish example of [-vn] > [-von], as noted by Roman Rausch in his Historical Phonology of Goldogrin (HGP/§3):
As suggested by Roman Rausch, this seems to be part of a larger trend in Gnomish of final syllabic [-ṇ] becoming [-on], for example:
Thus, it seems that n-syllabification was similar in Gnomish as it was later in Sindarin/Noldorin and produced the same vowel [o], but there were a few more possible combinations (such as [-ln]). As with Sindarin/Noldorin, final -rn is very common and remained unchanged, but there is at least one other example where syllabification did not occur: G. tathn “number” (GL/69).
In the Early Noldorin of the 1920s, there are no examples of -fon or -von, but a couple examples of -fn [-vn]: ᴱN. lafn “animal” < ᴱ✶labna (PE14/70) and ᴱN. nofn “down, set” (PE13/151). Perhaps final n-syllabification did not occur in the 1920s, but this could simply be lack of examples, as with Sindarin.
|After||02300||short final vowels vanished||ᴹ√KYÉLEP > celefn > N. celevon||Ety/KYELEP|
|After||06100||non-initial [m] usually became [v]||ᴹ√KYÉLEP > celefn > N. celevon||Ety/KYELEP|
Phonetic Rule Elements
N. final [vn] sometimes became [von]; [-vn] > [-von]
|After||02100||short final vowels vanished||ᴹ√KYÉLEP > celefn > N. celevon||Ety/KYELEP|
|After||05300||non-initial [m] usually became [v]||ᴹ√KYÉLEP > celefn > N. celevon||Ety/KYELEP|
Phonetic Rule Elements
Phonetic Rule Examples
|dravn > dravon||-vn > -von||ᴹ√DARÁM > dravn > N. dravon||✧ EtyAC/DARÁM|
|kelevn > kelevon||-vn > -von||ᴹ√KYÉLEP > celefn > N. celevon||✧ Ety/KYELEP|
|l̥evn > l̥evon||-vn > -von||ᴹ✶lebnā > N. lhevon||✧ Ety/LEB|