ARRIERE n.
"That which is behind"; the rear; -- chiefly used as an adjective in the sense of behind, rear, subordinate. Arriere fee, Arriere fief, a fee or fief dependent on a superior fee, or a fee held of a feudatory. -- Arriere vassal, the vassal of a vassal.
BACK n. 7 definitions
In human beings, the hinder part of the body, extending from the neck to the end of the spine; in other animals, that part of the body which corresponds most nearly to such part of a human being; as, the back of a horse, fish, or lobster.