压箱底

压箱底

Literally means:

putting something at the very bottom of a chest

Actually means:

Literally it means putting something at the very bottom of a chest. It figuratively describes a thing or skill that is considered so precious that it is kept as treasure and is rarely shown or revealed to others.

It also refers to something that is seldom used or something useless, and is thus put aside. Commendatory.

放在箱子的最下面。形容东西或技艺像宝贝一样收藏起来，不随便让人家知道或看到。也指东西不用或没有用处而被放在一边。具有褒义色彩。