Languages. A favorite topic of mine, indeed.
We have no idea what, if any, language family(s) the Matari languages are descended from, or even if they have anything at all to do with our languages in the here and now. However, a few things to consider:
Minmatar languages are certainly varied. The "tribes" seem more akin to what we would label as "tribal groups" rather than as "tribes" in the sense we tend to think of them, and all members of a tribal group would probably speak related, but not necessarily identical, dialects of the same language. My mother was Roma, and the Romani people are a good example of such a culture group; the language varies quite widely depending on location, mostly due to inclusion of loanwords from surrounding languages, but also due to simple dialectical differences.
Amarrian loanwords, as well as Gallente to a lesser extent, would likely fill Matari language, and some attempt would almost certainly be made at some form of standard Matari, even if it were little more than a "Minmatarized" Amarrian or Gallente.
Local dialects would be interesting; The Sebiestor, for example, being from the polar regions of Matar, would likely have lots of words for "snow" or "ice" but very few for "sunshine".
I had always imagined that Sebiestor was patterned after a norse language, with similar structures, due to the apparent mythological similarities, but meh... who knows.