countersign 的词源

“军队的口令，士兵在岗时发给的信号，只有先给出该信号的人才能通过，”这个词最早出现在1590年代，源自法语 contresigne，由 contre-（意为“反对”，参见 contra-）和 signe（意为“标志”，参见 sign (n.)）组合而成。

COUNTERSIGN. A watchword used by military bodies as a precaution against an enemy or enemies. The countersign may be changed at any moment, or any number of times, but is usually altered each twenty-four hours. It is given primarily to commanders of guards, and outposts and their sentries, to reconnoitring and visiting patrols, and to the field and regimental officer of the day. All others desiring to pass through the lines must first be supplied with the countersign, which is thus a guard against spies, strangers, and surprise. ["New International Encyclopaedia," 1906]

COUNTERSIGN（口令）。军队用来防范敌人的警戒口令。这个口令可以随时更改，通常每二十四小时更换一次。它主要发给警卫指挥官、哨所及其哨兵、侦察和巡逻队，以及当日的野战和团级指挥官。所有希望通过防线的人都必须先获得口令，这样可以防止间谍、陌生人和突袭。——《新国际百科全书》，1906年

此外，counter-sign 意思是“在另一签名旁边签名，或额外签名”，这个词出现在1690年代，源自15世纪法语 contresigner。可以参考 counter- 和 sign（动词）。相关词汇还有 Countersigned 和 countersignature。