What is "popular discipline"? [closed]
Solution 1:
popular, deriving from Latin populus (the people), is not always to do with being liked by many. It has a more general meaning that is relevant here.
popular = "involving or relating to ordinary people or to all the people who live in a country or area"
Cambridge dictionary
"popular discipline" therefore referred to the disciplined (organised and orderly) behaviour of the general population at that time.