Don't know if many people noticed the poll about the origin of നെയ്യ്.
I was surprised to find (in Gundert) that നെയ്യ് is the തത്ഭവം of സ്നേഹം. The first meaning of സ്നേഹം in Sanskrit is oiliness, or greasiness. Presumably, the word came about as: സ്നേഹം -> നേഹം -> നേയം(?) (because there is no ഹ in Tamil?) -> നെയ്യ്.
[I have to admit that I highly suspect this etymology - just because the word roots and the meanings match does not mean that one is derived from the other. E.g. consider "one" and "ഒന്നു". Very similar and identical in meaning, but they have entirely different origins (the former comes from Proto-Indo-European root *oinos and the latter is purely Dravidian).
This also reminds me of similar claims that some Sanskrit words were derived from Tamil - ഇഷ്ടം from ഇടുതം, കഷ്ടം from കടുതം etc. I read about these at a website but I am equally uncomfortable with the argument]