ar·ri·ère-ban 
(ăr′ē-âr-bän, -băn)
(ăr′ē-âr-bän, -băn)n.
1. A medieval royal proclamation by which vassals were summoned to military service.
2. The vassals summoned.
[French, from Old French ariere-ban, alteration (influenced by arere, behind) of herban; see koro- in the Appendix of Indo-European roots.]