By the way, I always found it strange that in DSC, they talked about the
mirror universe people from the "Terran Empire" as Terrans - because we
are Terrans too, so the difference is not clear, and it was even more
difficult to translate that into the Klingon subtitles.

I don't know what you ultimately chose to do, but these would just be tera' wo' and tera'ngan — and any ambiguity would be completely justified, since the humans of the Terran Empire are just as much Earthlings as the humans of the United Federation of Planets.

-- 
SuStel
http://trimboli.name