Hey guys, I know it's hard and I'm asking a LOT from you with this, but let's get out of the WC universe for a minute, into the programmers HEADS, shall we?
There! Now could it be possible to imagine, for just one second, that the programmers had really no idea on what names to give to the new cruisers (considering WC II was released very shortly after WC 1, I have heard), and just slightly changed the spellings from WC I, from "_thi" to "_tha"...
It makes sense, right?
Or perhaps they wanted the players of WC I to stay accustomed to the ship classes from WC I.
Follow my reasoning: in WC I we hear "Salthi", we think of light fighter. "Hey, why don't we keep that, the programmers must have thought, and make it "Sartha", so it still means light fighter in WC II?"
Guess what?
Jalthi-heavy fighter, Jalkehi-(surprise)heavy fighter. Dralthi-medium, Drakhri-medium.
Ralari-destroyer, Ralatha-destroyer
Fralthi-carrier, Fraltha-carrier...
Do you see?
Now probably AFTER WC II, the programmers decided that this thread was not a too original one to follow, so they decided to change the names more (Sartha->Darket, Drakhri->hey back to Dralthi (IV), etc...)