it's not that uncommon in fiction to have terminology that's almost, but not entirely like the equivalent in the real world.

Hm... That doesn't strike me as true, actually. Can you think of an example or three?

EDIT: Actually now that i think of it, this can be true for when an author is creating an alternative reality but wants things to be familiar to the audience. Like in Dragon Age, all the titles of the nobility and such things are similar to real-world terms for no special reason. But then compare Warhammer 40k, which is not an alternative world but rather a far future of ours: a computer is a "cogitator" and a camera is a "picter". Clearly different words, but rather than complete inventions, they're obviously based on somewhat plausible alternative etymologies.

However, that doesn't apply to a story like this, which is trying to logically follow from its starting premise, and in which the formation of the terms happens wthin the story itself. It's that plausible etymology that is lacking.