三长 = three long
两短 = two short
If you have just learnt Chinese language, you may be wondering, is 三长两短 an idiom? Three long and two short do not make any sense.
Furthermore, 三长两短 means death in Chinese language. What?! Why does 三长两短 mean death?
This has to go back to China history; Chinese people think that a dead person is to be put into the coffin. The components of the coffin are made of two short planks at the front and back, and three long planks at the two sides and the bottom before the coffin is covered up. Thus, the five planks make 三长两短 and are logically linked to death.
In addition, 三长两短 also means an unexpected misfortune, accident or disaster that causes death.
Now that you know the meaning of 三长两短, please do not simply use it to make fun of people. On the other hand, Chinese people use 三长两短 as a subtle alternative to 死亡 (death). By the way, as a Chinese who has grown up in a traditional Chinese family, I do not celebrate my 32nd birthday. Do you know why?