[Shadbase]

I like the most widely-known ones for some of the classes, those being:
Kensei = Wastelander
Hexer = Grimweaver
Priest = Gleamweaver
Ghost = Mirage

Gleamweaver and Grimweaver just have such nice rings to them, and gives them some more... man I don't even know the words.

Personally, I like just making up my own words for stuff too, n it feels really liberating to be able to NOT call my character a "redtail". Given the Japanese-themed character I ended up making (because woohoo! Weeaboo!), I tend to have some more Japanese centric names for stuff.
Kensei is "Samurai", Void Assassin is "Ninja" (or just "Assassin", depending on context), Priest & Lanternbearer are "Kannushi" if they're acting under any sort of 'god' rather than just light/element mages, Summoner by any name is "Spiritcaller", stuff like that. It's actually kinda hard to think of good names for classes and stuff, so I can kind-of imagine people just not calling them by their class names either...
Of course races are super easy, at least when it comes to the animals. Kitsune, nekomata, inu, tori... but it's also kinda just more understandable to call them "dogboy" "catgirl" "animal fucker", w/e...

Though in magic, it's just kinda... the -mancy names. It's kind-of the most obvious choice and are super common - even people in Sigrogana still use them sometimes, because other than Huggessoa and Mercala it's... kinda a toss job trying to remember the primordial element gods.