quintain
/ˈkwɪntɪn/noun
1- historical a post set up as a mark in tilting with a lance, typically with a sandbag attached that would swing round and strike an unsuccessful tilter〈史〉矛靶。
1.1
the quintain
the medieval military exercise of tilting at such a post（中世纪）持矛刺靶军训。
词源
late Middle English: from Old French quintaine, perhaps based on Latin quintana, a street in a Roman camp separating the fifth and sixth maniples， where military exercises were performed （from quintus 'fifth'）.