What does this idiom mean to teach fish to swim?

Basic explanation

Dancing in front of Luban with an axe. Showing off one's skills in front of experts. ?

derogatory sense

tidy

Song Ouyang Xiu's Book with Mei Yu Sheng: "Yesterday is really fixed; There are seven or eight poems; Record it today; Teach fish to swim; Ridiculous. "

example sentence

I am not an expert in literature and art, and I dare not talk about literature and art in front of an old "artist" like you.

General regulations

Lu Ban was a native of Lu during the Warring States Period. He is an expert in making exquisite instruments. People call him an "able man", and people always regard him as the ancestor of carpenters. Who dares to show off his axe skills in front of Lu Ban, that is to say, to show off his skills in front of experts? This ridiculous behavior of being too modest is referred to as "playing axe in front of Lu Ban" or "playing axe in front of Lu Ban". This is similar to the saying of "playing broadsword in front of Guan Gong".

In fact, the idiom "teaching people to use an axe" took shape as early as the Tang Dynasty. Writer Liu Zongyuan has such a sentence in a preface: "Fuck the axe at the door of the class, Yaner!" It means too thick-skinned to show off the skills of using an axe in front of Lu Ban and Ren Ying (also skilled axe hands).

This idiom is sometimes used as a word of self-modesty, which means that you dare not show off your skills in front of experts.