Aide

wiktionary

ref

Borrowed from French aide("aid; assistant", as in aide-de-camp(“field assistant”)). More at aid.

etymonline

ref

aide (n.)

"officer whose duty is to receive and communicate the orders of a general officer," 1777, short for aide-de-camp (1660s), a French term in English, literally "camp assistant" (see aid (n.)). Plural of the full term is aides-de-camp.