Aide-de-Camp
This is literally French for “aid in the [military] camp” or “camp assistant.” It’s a title for the assistant of someone with high rank.
Almost all references I saw had a military or royal context to them. The civilian title would be “administrative assistant” or “chief of staff.”
The pronunciation in French or pretentious English is “aid-de-COM” (no “P” sound on the end). In American English, it’s pronounced just like it looks: “aid-de-CAMP.”
Why I Looked It Up
It came up in a couple books I was reading. I understood it from context, but I was curious on the translation, and if there was any formal definition. There’s no standard to it, outside of the military implication.