40 m broadsword. What stem?

40-meter broadsword is a very popular network language. The meteor shower with a 40-meter broadsword first appeared in the headlines of Tencent News. Maybe the editor made a mistake by mistake. When editing, he accidentally wrote the length of the knife in centimeters. After seeing such an exaggerated statement, many friends draw some simple pictures in minutes to show how long a 40-meter-long knife is. Later, the meteor shower was extended. For example, some people can cut each other with a 40-meter broadsword even if they run 39 meters. Because the 40-meter-long broadsword is very exaggerated, netizens may have such expression packs when describing very exaggerated things.