teach (one's) grandmother to suck eggs

To try to teach an older person who is wiser and more experienced and wordly than a young person may think. Why are you explaining basic typing to Ethel? Yes, she's 70, but she's been using a computer since before you were born—quit teaching your grandmother to suck eggs.

Common Names:

Name	Pronounced	Usage
Tadeo	tah-DE-o	Spanish
Dragana	-	Serbian, Croatian, Macedonian
Zula (1)	-	Polish (Rare)
Ali (2)	AL-ee	English
Kayla (2)	-	Yiddish
Shevaun	shə-VAWN (English)	Irish, English (Rare)