The term "subordinate" has been used many times in this blog.
I don't like it at all, but it seems to be popular among some supervisors, and is not limited to the military.
In fact, it will be found in many personnel and P&P manuals. It was in the employees guide for my former employer (local government). When I was hired, nobody seemed to worry about it much. Even our supervisors were more like co-workers. We worked well and we got along well.
But new administration came along with a completely different attitude. We were *definitely* underlings then. I retired.