I think this is the key point with the names.
They're romanised versions of terms from an Alien language.
Thargoid sound based communication is very different to ours, and inherently has to be so. (Assuming the insectoidness of the Thargoids extends to respiration, then they don't have lungs, windpipes or vocal chords.)
TDW does actually set it out that way when it talks about the Oresrians:
"... he found himself standing behind two tall, violent looking insect-forms, their bodies armoured in light grey, their facetted eyes swivelling to stare at him as they talked together, chelicerae clashing and clacking in their peculiar form of communication."
OoTD confirms and extends it.
"The keening was a constant back-ground, but Carl seemed unaware of what it meant. He remained intent on the stream of clacking."
"'Incredible aren't they?' Carl's words were softer now, almost tender. He made an extended series of glot-stops, clicks and whistles."
Still a few options I guess:
- Conversion into our style of vocalisation and language done by the Oresrians/Thargoids
- Conversion into our style of vocalisation and language done by humans
Coming back to Jaitou's point, the 'ian' bit does seem like it would be an artefact of conversion into our language and terminology rather than a romanisation of the sound made by the Oresrians/Thargoids.
I guess whether anything can be drawn from the Oresr, Klaxx parts are completely up for debate at this point. It doesn't really seem that way, as Oresr and Klaxx don't appear to have any meaning, or be the names of places, so it wouldn't seem to be 'the beings from the place humans call Oresr and Klaxx', but you never know, names change and things get lost. Also if things were of that nature then it would be pretty sensible to change the names in the records and history books to stop random people heading to those locations, and getting themselves killed or starting a war.
Also, as a complete aside to the names, I've said it before on the Alien megathreads, but I strongly suspect that the Thargoids use of morse ties in to the nature of their form of vocalisation, more specifically it would be more naturally intelligible to them and reproducible by them than human speech in terms of the actual sounds used.