I don’t know Jill Biden. But I know Jill Biden.

All of us “Philly girls” know Jill Biden.

We are Jill Biden.

We female Fightin’s take care of the job. Just as, on a Super Tuesday stage behind a speechifying former Vice President Joe Biden this week, his raised-right-down-Broad-Street-into-Willow-Grove wife did exactly that: She got into a Philadelphia Eagles lineman defensive crouch and laid her hands on a vegan-activist-protester storming a stage in Los Angeles behind the front-runner for the Democratic presidential nomination.

I watched this viral moment and had just one thought, one Philly girl to another:

Of COURSE you take care of business this way.

OF COURSE you then turn around in your skirt and jacket and take even more control by shouting: “We’re OK!” And, OF COURSE you clap your hands as if nothing just happened, letting the crowd resume chanting for the guy who just scored huge primary nomination wins. No sweat.

No surprise in my zip code, at least, that Jill’s body-block reverberated across social media. The former Jill Jacobs, Upper Moreland High School Class of 1969, had just done what a Philly Girl does. No matter that she has spent years as an English professor with a Ph.D. and other advanced degrees.

Jill. Is. No. Snowflake.

A few days earlier, she’d caught my attention by helping remove a pretty sizable male heckler from a New Hampshire rally. When asked about that one, her response to reporters was, with a laugh: “I’m a good Philly girl.”

No kidding.

Joe surely knows where this grit comes from. He was once a young boy from Scranton, Pa. (Don’t know Scranton? Look up Philadelphia, add coal mines and mountains.) At a California fund-raiser Wednesday night, he shot out this zinger about his wife’s Tuesday tussle on stage in front of rolling cameras:

"I’m probably the only candidate running for president whose wife is my Secret Service,” the former U.S. senator and No. 2 to President Barack Obama said, according to The Hill. “Whoa. You don’t screw around with a Philly girl, I’ll tell you what.”

Willow Grove, on a map, is in a belt of Philly suburbs that share with one another a certain old-school, working-to-middle-class cultural DNA. To test this theory, I drove there to talk with a wise man of Jill’s generation.

He’s wiseacre Jerry DiMarzio, Upper Moreland Class of ’70 — just a year behind Jill. His family has run the Willow Inn since after his mother had a priest come to the former brothel to bless and douse it with holy water so she could turn it into an Italian restaurant and pub.

He still talks about how Jill’s dad gave him his first mortgage. How he was the kind of man who enjoyed a game of pool and darts.

“I’m gonna say most of the girls here were nice girls, but they weren’t wearing silk and lace or that,” said DiMarzio, who at 69 is quick with a one-liner.

Back then, the small single houses around here were full of former Philly folks like Jerry’s mom, from Germantown, or blue-collar carpenters who became big-time builders with all the open land out there.

The girls around there, Jerry said, “they wouldn’t take any crap. But they wouldn’t give you any crap if it wasn’t called for.”

I knew it.

He and I talked in a vintage-red tavern booth in a building that’s more than a century old.

“I’m here," I told Jerry, "because I have a theory.” Told him how I grew up in Upper Darby. The Philly Girl reflex, I told him, seems baked in us.

“It’s in the DNA,” I said. “What do you think?”

DiMarzio, a 5-foot-4 sparkle of gab who’s married to a 6-foot-tall brunette named Jan, leaned back and thought about it. Only after smiling did he offer his own theory: “Let’s call it wooder.”

This hunt-or-be-hunted stuff, though, isn’t in everyone. It was forged in the non-silver-spoon zip codes in and around Philly, back when union folks lived out there. Places like Willow Grove and Horsham, Oxford Circle or Southwest Philly, Upper Darby (Go UDHS Class of ’88!) or Aston.

These places branded you with unmistakable characteristics: 1) A no-nonsense Philly accent that sounds like a schoolyard challenge at all times. 2) An always-be-alert defensive reflex that, at least as it came out of the mouths of my own public school classmates, went like this: “I’ll kick your a—.”

In an email the New York Times obtained and published earlier this year while profiling Jill, she mentioned these ordinary-kid roots. She was writing to a colleague at Northern Virginia Community College, where she taught until a few months ago. The Times got the emails through a records request. Here’s what the Times reported:

In January 2017, Dr. Biden wrote about the personal transition that came with her husband’s departure from public office.

“I am currently living in 3 houses!” wrote Dr. Biden, whose emails show up as “Jill Tracy.” “I can’t find a thing!!! I have my DE home, our new rental, and the Vice President’s Residence all this for a middle class girl. Amazing.”

Jerry and I laughed when I pulled out my iPhone and zoomed in on the photo of Jill with her hand gripping the protester. He always remembered Jill as more refined. Then again, this was Upper Moreland.

“Would a woman raised in Rittenhouse Square," I asked, “have had the same moves as Jill on that stage?”

This time, no pause from Jerry.

“If you get her silver spoon out of her mouth on time,” he said. Again, though, a smile. “That’s a different kind of cloth.”

Exactly my point. Bless the girls with the grit.