Your mama is not the same thing.
Teaching your grandmother to suck eggs is a phrase of antiquity dating further back than the 1700s.
It refers to the practice of eating raw eggs which was common at one time. I remember people eating raw eggs when I was young. Being from the South, we cook everything well done. Considering the heat we have, I imagine the practice is a protection from food poisoning.
Anyway, it means for a novice to instruct someone much more learned. I like the variation of the gosling showing the goose the pasture.
Teaching to the choir is another variant but it really refers to lecturing someone already in agreement.
Repeatedly, I came across the exact phrase in the paragraph below but did not get the original source but I am pretty sure it originally came from Hog on Ice by Charles Earl Funke (Harper & Row, New York, 1948). I found the book on Amazon.
"One of the earliest of these is given in Udall’s translation of ‘Apophthegmes (1542) from the works of Erasmus. It reads: ‘A swyne to teach Minerua, was a prouerbe, for which we sai: Englyshe to teach our dame to spyne.’” That last bit was about an expression, don’t try to teach a dame to spin."
Now for Americans, "go suck an egg" means get lost and we know how we disdain an egg sucking dog. My aunt throw extra eggs from her henhouse on a tree stump for her dogs to eat. Times have changed.
I follow a folktales listserve out of England and some Americans were insulted by an email titled, "Go tell your grandmother to suck eggs." I can understand how it was misunderstood. But folks interested in folktales know things can mean different things at different times in history.
I didn't comment or apologize. But I know some Americans who told some Brits to tell their grandmothers to suck an egg.
What phrases have you heard of that means the same as a "gosling showing the goose the pasture".