From Joel Martinsen's English translation of Liu Cixin's The Dark Forest (page 231 in my paperback edition):
Einstein said, "I have thought this over for a long time, and I believe that the Lord's fear of Luo Ji has only one possible reason: He is the mouthpiece of certain power."
Qin Shi Huang shut down further discussion of the subject: "Don't get into that. Instead, let's think of how to fulfill the Lord's command."
Like many other terms in Martinsen's translation, this seems to be an overly literal translation of some Chinese phrase which I don't know, and which might have been intended to be obscure in the original too. But unlike some of those other phrases (e.g. "chains of suspicion"), the characters in-universe don't seem to be puzzled by the phrase, which makes me think it was just poorly translated.
If it had said "...of a certain power," I wouldn't even ask; I'd just assume it was meant to refer to some faction implicitly known to the ETO members talking here but intentionally mysterious to the reader. Without the a, I'm puzzled.
What was the original Chinese phrase, and (to be best of your knowledge and/or wild guess) what was it intended to mean in this context?