chAndogya upaniSad 1.1.8 and 8.3.5

[Sudalaimuthu Palaniappan]

I have come across two interesting verses in chAndogya upaniSad. 1.1.8
states:
"tad vA etad anujJAkSram, yaddhi kim cAnujAnAty aum ity eva tad Aha;.....".
S. Radhakrishnan translates this as "Verily, this syllable is of assent, for
whenever one assents to anything he says simply 'aum'.....". It is
interesting that in Tamil we have "Am" (DEDR 333) which is an interjection of
agreeing. In Sri Lankan Tamil dialect, it becomes "Om". DEDR compares this
with Sanskrit "Am" meaning "yes", and Pali Pkt. "Ama", etc. It also lists an
entry in Comparative Dictionary of Indian Languages (1235) and an article by
Parpola in ABORI vol.58-59 (1977-78) pp.251-52. Does anybody know what the
current scholarly consensus on the etymology of "aum" is?

Verse 8.3.5 says, "tAni ha vA etAni trINy akSarANi sat-ti-yam iti; tad yat
sat tad amRtam, atha yat ti tan martyam, atha yad yaM tenobhe yacchati yad
anenobhe yacchati tasmAd yam, ahar ahar vA evaM  vit svargaM lokam eti."
Radhakrishnan translates this as "Verily, these are the three syllables sat,
ti, yam. The sat, that is the immortal. The ti, that is the mortal. The yam,
with it one holds the two together. Because with it one holds the two
together therefore it is yam. He who knows this goes day by day into the
heavenly world."

I was very surprised by the use of the form "sattiyam" to etymologize the
word "satya". In Tamil, Sanskrit "satya" becomes "cattiyam" which is often
pronounced as "sattiyam". If a modern Tamil speaker who is not aware of the
Sanskrit source, is asked to etymologize the word, he will probably start
with the same form. brhadAraNyaka upaniSad 5.5.1 uses "sa-ti-yam", a very
similar form. Does the use of these Prakritized or Dravidianized forms to
etymologize Sanskrit words imply that the authors' own mother tongue was
Prakritic or that the Prakritic forms were very current or acceptable in
UpaniSadic times?  Thanks in advance.

Regards

S. Palaniappan