Their protest was just a popgun, failing to get any attention from the government.

popgun 是复合词，由 pop（拟声词，表示"砰"的声音）和 gun（枪）组成。字面意思是"发出'砰'声的枪"，实际指"玩具枪"，比喻"虚张声势但毫无威力的东西"。