Teach fish how to swim is an idiomatic expression derived from the Latin proverb . The phrase describes the self-sufficiency of those who know better how to do everything than the experts. It corresponds to the expression, "teaching grandmother to suck eggs". Erasmus attributed the origins of the phrase in his Adagia to Diogenianus. Read online: ; compare Ἰχθὺν νηχέσθαι διδάσκεις
A corollary idiomatic phrase is part of common usage in Chinese ""Muehl, Louis Baker et al. (1999). ; 班门弄斧: display one's slight skill before an expert e.g. 在你面前班门弄斧,太不好意思了 (I'm making a fool of myself trying to show off before an expert like you)
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