If I described a situation as being like “something from the Keystone Cops,” would you have any idea what I was talking about? Would you think the Keystone Cops were good? Bad? From Pennsylvania? Would you want to defund the Keystone Cops?

The Cops — or “Kops,” as they were sometimes spelled — were bumbling bit players from the silent movie era, a creation of Mack Sennett’s Keystone Film Co. They debuted in 1912: inept, if energetic, cops, a half-dozen of whom would explode into a room and swarm around, accomplishing nothing.

I’m pretty sure no one alive today saw the premiere of a Keystone Cops film, yet the ensemble’s name symbolizes chaotic incompetence.

Or it did, anyway. I recently wrote about cultural references that expire and invited readers to share their own examples. Reau Koffman is a doctor on the faculty of a teaching institution in Ohio. While on his rounds with medical students and residents a few years ago, he discussed a situation that seemed a little chaotic.

“I remarked that it made us all look like the Keystone Cops,” he wrote in.

No one had a clue what he was talking about.

Wrote Reau, 61: “I’m sure I heard the reference from my parents and likely saw clips on television or old movies, and I am sure they were long gone years before I was born.”

Reau polled his three daughters — born in the early to late 1990s — and none had heard of them. His wife — born late in the Eisenhower administration — didn’t know either.

The Keystone Cops have become a sort of touchstone for Reau, a reference he trots out with younger people. It mostly conjures blank stares, leading him to believe “there is apparently no shorthand phrase for chaos and incompetence exhibited in a slapstick manner for the current generation.”

Or maybe today’s generation has its own term. Perhaps instead of “This makes us look like Keystone Cops,” they say, “This makes us look like we planned Fyre Festival.”

Baltimore’s Claudia Sumler was getting help with a computer problem from a college student recently. “In passing, I made a reference to ‘The Maltese Falcon,’ ” Claudia wrote.

The college student gave her a blank look.

“I hesitantly said ‘Humphrey Bogart?’ ” Claudia wrote. “Never heard of him.”

Claudia was shocked. “The Maltese Falcon” — released in 1941 — was already an old movie when she first saw it while in college in the late 1960s. Humphrey Bogart had been dead for years.

“But to discover that both had sunk into obscurity was hard to fathom,” Claudia wrote. “When I was the student’s age, I had never seen Sarah Bernhardt in a play, but I certainly knew who she was.”

This reminds me of a meme I saw the other day: Today’s 90-year-olds were 10 when Pearl Harbor was attacked. And people who were 90 when Pearl Harbor was attacked were 10 years old in 1861, when the American Civil War started.

Makes you think. (I’m not sure what it makes you think, but you are thinking, aren’t you?)

Susan Hale of Kent Island, Md., said no one knew what she meant while talking to her 20-something grandnieces and their boyfriends. They were all looking at an old photo of Susan’s now-50-year-old daughter.

Susan said to them: “That was her Boy George haircut.”

The response: Boy who?

It isn’t just cultural references that fade. A few years ago, Fred Goodman of Montgomery Village, Md., gave a presentation at work. At the end of one slide, a colleague asked a very perceptive question. Fred said: “Well you’re the perfect straight man, because that’s what I’m going to talk about next.”

No one under 40 understood the reference.

“Apparently the concept of a comedy duo is dead,” Fred wrote. “They thought a ‘straight man’ was a reference to sex. I might as well be Aristophanes!”

Aristophanes is a reference to my previous column, where I mentioned that classics scholars still debate what certain lines in the Greek’s plays mean.

When Jim Ashley’s kids entered the dating age, he regaled them with the story of meeting the mother of one of his girlfriends. The mother’s identical black cats were called Carbon and Copy. Jim asked the mother how she told them apart, only to get the withering answer, “Carbon is a boy.”

Jim’s kids were unmoved by his tale. “All I got at the end of the story were blank looks followed by me needing to explain what a carbon copy was,” wrote Jim, of Arlington, Va.

Frank Parente of Falls Church, Va., was once at a staff meeting when his boss asked him to respond to a letter that came in “over the transom.” Wrote Frank: “Some younger colleagues didn’t know what that meant.”

I wonder: Would you call something that comes in over the transom a transom note?

Twitter: @johnkelly

For previous columns, visit washingtonpost.com/john-kelly.