I had a co-worker named Kimberly. Her older sister was Kim. Their mom was born and raised in China, and thought they were two different names.
Hehe, in the family across the alley, all three are named some variation of Chris. That makes things pretty easy to remember, at least.
Madison took off, apparently because it was the name of the main character in Splash, (1984) and she took it from “Madison Avenue” in the film. (Caveat: I’ve never seen the film.)
When the film was released, just before Reagan defeated Mondale, there was a lot of grumbling about the electoral college-- which there always is before a presidential, it’s just that I was 17 when the movie came out, and aware of the grumbling for the first time. I was dumb enough to think all the little Madisons were being named after President James Madison, as a protest, because Madison had not been in favor of the electoral college. 
Shirley Temple.
She sealed the name’s fate.
The name was at one time exclusively a boy’s name, then Charlotte Bronte wrote a book called Shirley, about a tomboy who grew up to be a tough and self-sufficient woman.
She was defiantly named “Shirley” by her father (it would be like naming a girl Connor, Apollo or Brayden today), who wanted a son, and proceeded to treat the girl as one would a son, in a time when sons and daughters were treated very differently.
The book was hugely popular, and soon there were little girls named Shirley everywhere.
The name existed as a “Robin,” or “Avery” for a while, but with most boy Shirleys named after a father or grandfather, and girl Shirleys by parents looking for something “modern.” Then Shirley Temple made her film debut (1932), and shot dead forever the name as a name for boys, no matter how beloved (or rich) great-grandpa Shirley is. That’s why the name disappears from the boys’ list then.
However, in the 1950s (The Honeymooners), there would still be men around named Shirley. They would have been born before 1932, but The Honeymooners was on in 1955 & 6, so a man named Shirley could be as young as 23-- and easily the age of the main characters.
Thanks for that outline. Which highlights the point that strong cultural expectations to name newborns after parents, aunt/uncles, grandparents, etc., acts as a very strong gender stovepiping of names. And also serves to slow or stop innovation in names. Like the person upthread who claims to be a fourteen. That’s some serious name stasis there.
As those outmoded customs die off, names become a lot more freeform. And can evolve quickly and jump between the sexes quickly. Which is all to the good in my book.
one of the few names that crossed the male to female back to male line is douglas/douglass.
[Douglas (given name) - Wikipedia]Douglas (given name) - Wikipedia
typically, once a male name flips it doesn’t flip back.
Yep. I saw the movie and have watched the name grow in popularity markedly since then
Back then I used to hear a lot of comments along the line of “Will people ever take a woman named Madison seriously as a judge or politician?”
Well, it happened.
Yeah. It doesn’t even ping my “that’s an odd name” radar anymore
On the other hand, Jonathan and John are two different names.
Nor do names that started off as female become male, nor do they get male variants. The closest I can think of is “Mario” or “Marius”, which did originate as a male name in itself, but which is also often used to honor the Virgin Mary.
There are a lot of "Maddie"s at my school, but they’re about evenly split between Madisons and Madelyns.
Oof, when I was a lad in elementary school Madelyn (or whatever spelling variant) was an old lady’s name. In fact, lots of old lady names have come back in my lifetime, but Gertrude, Myrtle and Flossie remain in the graveyard.
I know one Gertrude who is about 30yo. And was born and named here by non-immigrants. So home grown Americans.
Which origin matters only insofar as I/we don’t know that there may not be other countries where it’s a currently popular name, or was one those parents would have thought ordinary in their culture 30 years ago when they chose it.
I know a couple who named their daughter Gertrude about 8 years ago, but were always quick to say “We’re calling her ‘Trudy.’”
My first thought was “They’re Monk fans.”
My second was “Was that Trudy’s full name?” 
I jokingly suggested to my son that he should name my youngest grandson in a salute to the classics – Elmer, Homer or Pinkney. Instead, we got a Liam, a name I understand to be fairly popular right now.
Or Brokenwood fans. We love Trudy on that show. But 30 years ago is too long.
I had a great-aunt named Gertrude, born in the 1890s, but she was known as Gert, for short. Also, there was Drew Barrymore’s character in ET – Gertie.
And it’s NEVER short for William. Do not even suggest this.
In L.M. Montgomery’s Anne of Green Gables series of books, Anne grows up and has a number of children, one of whom is a boy named Shirley, after her last name. He would’ve been born around 1900 or so.