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
Saraid	-	Irish
Dickinson	['dikinsən]
Natale	nah-TAH-le	Italian
Magnolia	mag-NO-lee-ə	English
Sulayman	-	Arabic
Gervasius	-	Ancient Germanic (Latinized)