The expression which has a similar pronunciation with "Pizza Hut" in Chinese, is used to describe those who are above the normal marriage age but still single and need to keep struggling to find their other half. This group more often than not put so much time into work that they have little chance to meet potential partners. So they are considered to be people who are doomed to be single, and that’s where “doomed single” came from。

　　跟必胜客发音相同的这个“必剩客”是用来形容那些超过普遍的结婚年龄仍然单身，而且还得继续为寻找自己的另一半而奋斗的人们。这些人通常都把大部分时间用来工作，很少有机会遇到合适交往的对象。因此，他们都被看作是注定要单身的一群人。故称，“必剩客”。

　　For example:

　　John doesn't care much about being called “doomed single”， he said he enjoys being single。

　　约翰并不在意被称作“必剩客”，他说他很享受单身的生活。