！keep one's cool和keep cool在词义上有一样的，也有不同。

keep one's cool中cool为名词，中文意思是保持冷静

keep cool中cool为形容词，中文意思是保持冷静保持凉爽镇定自若

In ancient China， hand fans were almost the only ones to help people keep cool.

在古代中国，手扇几乎是唯一的帮助人们保持凉爽的工具。