I think that's how " witted" is a little bit different to just " quick" .

我认为这“智”与“快速”有点不同的方。

Quick-witted, we could just remove the word " witted" , a quick person is like intelligent, someone who thinks very fast.

智，我们“智” 这个词去掉，敏的人像聪明人一样， 思维非常快的人。