The Collaborative International Dictionary of English v.0.48:
Orderly \Or"der*ly\, a.
1. Conformed to order; in order; regular; as, an orderly
course or plan. --Milton.
2. Observant of order, authority, or rule; hence, obedient;
quiet; peaceable; not unruly; as, orderly children; an
3. Performed in good or established order; well-regulated.
"An orderly . . . march." --Clarendon.
4. Being on duty; keeping order; conveying orders.
"Aids-de-camp and orderly men." --Sir W. Scott.
Orderly book (Mil.), a book for every company, in which the
general and regimental orders are recorded.
Orderly officer, the officer of the day, or that officer of
a corps or regiment whose turn it is to supervise for the
day the arrangements for food, cleanliness, etc. --Farrow.
(a) The court of the commanding officer, where charges
against the men of the regiment are tried.
(b) The office of the commanding officer, usually in the
barracks, whence orders emanate. --Farrow.
Orderly sergeant, the first sergeant of a company.