Is the Etruscan word for lake, "tisś", derived from the word for water, "thi"?

Question

Is the Etruscan word for lake, "tisś", derived from the word for water, "thi"? The Etruscan word "tina" (a type of a vessel) is, as far as I know, thought to derive from "thi", even though there is an apparently unexplained change from 'th' to 't'.

EDIT: I don't think @Draconis answer to my previous question answers this question. Draconis wrote that "tusna" (swan) is probably related to the Proto-Italic word for "white", and is therefore unrelated to "tisś" (lake). That tells us nothing about whether "thi" (water) and "tisś" (lake) are related.

Answer 1

First, note that Fournet believes there was no phonemic contrast between t and th; he points out that the word for "community" is attested as both tuthi and tuti, among others. So that's not necessarily an issue.

Gordon (whose work is rather controversial but whose database is the most complete I know of) documents both naitis "lake" and neitisś "to the lake", suggesting that the root is simply tis and the ś is the directional case marker.

On tisś, Fournet draws a connection to Hurrian šiwe "water" and says "Etruscan would be a compound". He doesn't cover thi, but it seems entirely plausible that tis could be a compound of thi and something else. Certainly thi has plenty of attestations and we can be fairly confident in its meaning.

Ultimately, like most matters of Etruscan etymology, there's no way to know for sure. The corpus is just too limited. But we can say that it seems plausible, at least.