원래?

It is an adverb - originally. You could think of it as its synonyms depending on the context - generally, naturally, commonly - and it will make the translation more natural.

Maybe it could be more helpful if you translate it with the synonym “usually”

Q: do you usually not eat (breakfast)? A: that’s correct. I usually don’t eat breakfast.

(Usually when someone asks something like “do you not _____?”, I think it makes more sense if you translate the “네“ as “that’s correct” and the “아니요” as “that’s not right.” , since in English usually you use yes/no for the opposite meanings when answering those questions)

원래 suggests ‘by nature’ or ‘as a rule’

Q: As a rule, you don’t eat (breakfast)? A: Correct. I don’t eat breakfast by nature.

Q: You normally don’t eat breakfast? A: No, I don’t really eat breakfast.