jump out跳出，skin皮肤,那么jump out of one's skin跳出某人的皮肤,这其实是一个夸张用法，用skin指代魂不附体、受惊吓的状态，所以jump out of one's skin指的是“大吃一惊，欣喜若狂”。

【例句】
I didn't hear you come into the room and you made me jump out of my skin.
我没听见你走进房间，你吓了我一大跳。

I nearly jumped out of my skin when you dropped that tray; it made such a loud noise.
你把那只盘子掉在地上时，我几乎吓了一跳，声音那么大。