The "coffin board" in Shanghai dialect originally refers to an insect that looks like a cricket. Because its head is flat in front, it looks like a coffin board, and the cricket can't be used for fighting, so it is an ugly common name. In addition, Shanghainese also describe useless, space-occupying, flat-like things as "like coffin boards", which is derogatory. When swearing, there are also people who don't turn their heads, stand still or do things rigidly, and call them "like coffin boards."