Tom Bombadil
#1406
If this is Primitive Quendian or Common Eldarin, wouldn't we see for Sindarin
Ndangwetʰa > Ndanbetʰa > Ndambetʰa > Ndambetʰ > Ndambet > Dambet > Dambed > Dammed > Damed?
That is, if Old-Noldorin -tʰ > -t still applies. In PE/395, Ndangwetha isn't assigned a language; and I'd say it's more likely to be late Old Sindarin or early Middle Sindarin, formed at a time after w- > gw-, but before nd- > d- and with the PQ form of the second element being wetʰā. This would explain why gw didn't turn into b (the g- developed later, maybe by analogy), why the -a didn't vanish in CE (it was originally long) and why the -th remained (because it was at the time not final).