militia (n.)

1580s, "system of military discipline," from Latin militia "military service, warfare," from miles "soldier" (see military (adj.)). The sense of "citizen army" (as distinct from professional soldiers) is first recorded 1690s, perhaps from a sense in French cognate milice. Historically, the Anglo-Saxon forces that resisted the Vikings were militias, raised by counties. In U.S. history, by 1777 as "the whole body of men declared by law amenable to military service, without enlistment, whether armed and drilled or not" [Century Dictionary]. In early 19c. they were under control of the states, enrolled and drilled according to military law but not as regular soldiers, and called out periodically for drill and exercise and in emergency for actual service.

From:
https://www.etymonline.com/word/militia