Questions on word-final vowels in Sanskrit

[Sudalaimuthu Palaniappan]

Some of the words borrowed from Sanskrit into Tamil give information about how
Tamils perceived the pronunciation of some Sanskrit sounds. (If there was no
difference between their representation in Tamil, their perception of the
Sanskrit sound and the Sanskrit sound in reality, then it might say something
about the pronunciation of Sanskrit itself in Tamilnadu more than 1100 years
ago.) An analysis of pairs of words where most IA scholars agree on the
direction of borrowing as from Dravidian into Sanskrit suggest that the
converse may also be true.

Consider the following.

The word-final "a" in Sanskrit seems to have been perceived by Tamils in many
cases as close to the extra-short "u" in Tamil. For instance, the word "soma"
in Sanskrit has been rendered by periyAzvar as "cOmu" in the following line.

tUya nAn2maRaiyALar cOmuc ceyya  (Periya tirumoLi 2.10.1.6 or nAl. 1138.6)

(translation: with the pure ones of the four vedas performing soma)

Another interesting case seems to be where Sanskrit "kapAla" is rendered in
Tamil as "kapAl" as shown below.

vaittavan2 kapAl micai                            (tiruccanta viruttam 42.4 or
nAl. 793.4)

(translation: having placed on his skull)

This seems to be very unusual. Normally, one would expect "kapAlam". The
absence of any sound after "l" in the Tamil word suggests that the Sanskrit
final "a" was so imperceptible as to justify removing it altogether.
Alternatively, one could interpret it as the author hearing it as "kapAlu" and
removing the final "u" to make it sound literary. (Many literary Tamil words
are pronounced colloquially with an enunciative vowel often represented as
extra-short "u".)

Interestingly, there are Sanskrit words accepted by Indo-European scholars as
borrowing from Dravidian which show a final "a" while the equivalent Tamil
forms have final extra-short "u" or expected to have an enunciative "u"
colloquially as shown by the pair, Sanskrit karambha and Tamil kuzampu or
Sanskrit kuvalaya and Tamil kuvaLai (equivalent in pronunciation to kuvaLay).
(This does not mean Sanskrit word was borrowed from Tamil.)

I would like more information on the pronunciation of word-final vowels in
Sanskrit and what happened to them in MIA and NIA? Is there any research on
the presence or absence of enunciative vowels and their conditioning in
Sanskrit? Why is there such a mapping between Sanskrit -a and Tamil
zero/extra-short u?

Thanks in advance.

Regards
S. Palaniappan