what's his twenty? 这句话源自民用无线电台的呼叫语,类似卡车司机之间的相互呼叫。它的意思就是“What is your location? /Where are you?” 你在什么位置?。
类似的还有:
What's Your 18? = What type of truck are you driving? 你开的什么样的卡车?
Big 10-4 = I completely agree 我完全同意!
Go 10-100 = Go to the restroom 去洗手间
参考资料:http://www.cbslang.com/popular/