They were brown-bagging outside the stadium, hiding their bottles in brown paper bags.

brown-bagging 是由 brown bag（棕色纸袋）加上动词后缀 -ing 构成的现在分词形式。brown 指"棕色的"，bag 指"袋子"。 brown-bagging 这个动作源于人们用棕色纸袋隐藏酒瓶的行为，现在常用来指"用纸袋遮掩着喝酒"或"偷偷喝酒"的行为。