My Sainted Favorite Mother had a saying for as long as I can remember. If you were stating the painfully obvious or just trying to tell her something she already knew, she would lovingly snap "Teach your grandmother!" in lieu of the less polite and less cultured "Shut the hell up."
Or so I always believed. "Teach your grandmother", in this context, had a very obvious etymology: one's grandmother, it is assumed, is/was a wise, intelligent and experienced person, and any life lessons you might wish to impart to her have probably already been learned.
My Favorite Mother also had a favorite book series from when she was a kid, and she got all of us reading them as well: the Arthur Ransome series that starts with SWALLOWS AND AMAZONS, and ends, some twelve or thirteen books later, with.... something. I forget what. As a kid I ADORED the first two, and grew slowly less interested as the series went on. The first couple had to do with two sets of siblings who had learned how to sail little sailboats in the Lake District in England, and camped on an island in the middle of one such lake, and had wars and adventures and whatnot.
As an unrepentant tomboy myself I just loved Captain Nancy of the good ship Amazon, who was determined to be a pirate. Captain Nancy's real name was Ruth, but her uncle once pointed out to her that pirates were ruthless, so she promptly renamed herself Nancy. Which is the sort of joke that really appealed to Adolescent Mojo. But I digress.
(BTW, if you're too lazy to read the books do NOT judge them on the terrible, TERRIBLE 2016 movie version of S&A, which deviates from the book SO TERRIBLY there should be charges filed. The kids bicker cruelly, there's a nonsensical Russian spy subplot, the ending is just ...ugh. Oh, look, Martha, another digression!)
My point is, I was reading one of the books, entitled WINTER HOLIDAY, wherein the kids are in the Lake District in the middle of winter, and one of the Amazons was trying to row ashore but there was ice blocking her, and she was whacking the ice with her paddle while the other kids on shore were shouting Helpful Advice at her. To which she replied:
And Mojo, in her youthful adolescent triumph, thought, "Ah-HAH! So THAT's where Mom got that from!" And that's about as far as this anecdote goes.
Until a few weeks ago, when we decided to watch THE BIG COUNTRY, with Gregory Peck. I like Gregory Peck, but in this particular case we were on a Burl Ives kick. The very first record I ever owned was Burl Ives singing LITTLE WHITE DUCK; he was also famous for being the snowman narrator in the RUDOLPH THE RED-NOSED REINDEER Christmas special. So I always grew up thinking of this kindly bearded Santa of a man singing "Froggy Went a-Courtin'" and other childhood favorites. I was well into adulthood before I learned that he had a second career in the movies, essentially playing the same Evil Patriarch about a half dozen times. Of which THE BIG COUNTRY is a prime example. Burl plays the roughshod but ultimately honorable Rufus Hannassey, whose conflict with Peck's McKay ultimately leads to a duel, in which there is the following exchange:
This was a REVELATION for me. It turns out my mother's innocent-sounding phrase was EDITED FOR YOUNG IMPRESSIONABLE EARS! And if you Google "teach your grandmother", the egg-sucking part is invariably included. There's even a Wikipedia article on it!
So now I am SHOCKED. For my mother, as we were growing up, would have NEVER APPROVED of us using the whole sucking eggs thing. (It was a simpler time.) I had heard the phrase once or twice as a child, and never quite got what it actually meant, but it sounded dirty, and hence Not For Polite Company. Later on I saw a Disney movie in which a kid's beloved dog was accused of sucking eggs, which was considerably less dirty--since it was Disney--but apparently Very Bad Behavior For a Dog.
Anyway, once again a fond childhood memory is NOT WHAT IT SEEMED.