The Collaborative International Dictionary of English v.0.48:

Arriere-ban \Ar*riere"-ban`\, n. [F., fr. OE. arban, heriban,
   fr. OHG. hariban, heriban, G. heerbann, the calling together
   of an army; OHG. heri an army + ban a public call or order.
   The French have misunderstood their old word, and have
   changed it into arri[`e]re-ban, though arri[`e]re has no
   connection with its proper meaning. See Ban, Abandon.]
   A proclamation, as of the French kings, calling not only
   their immediate feudatories, but the vassals of these
   feudatories, to take the field for war; also, the body of
   vassals called or liable to be called to arms, as in ancient
   France.
   [1913 Webster]