napkin

n. 餐巾

He has much learning, but he hides it in a napkin.

他学识渊博，可是并没有把它发挥出来。

He is a lazy devil and keeps his talent in a napkin, with his ability and a little energy he could set the Thames on fire.

他是一个懒鬼，把天资埋没了。只要发挥出他的才干，再加上一点干劲，他可以干出一番惊天动地的大事来。