My 8 year old says it all the time.
Yep. That is what the term means to me- and Google.
A jump seat (sometimes spelled jumpseat) is an auxiliary seat in an automobile, train or aircraft,[1] typically folding or spring-loaded to collapse out of the way when not used. The term originated in the United States c. 1860 for a movable carriage seat.[2]
My family had a strong hierarchy among us kids so no one got to call shotgun. I first heard it when I was 16 and my friends and I got our drivers licenses.
Born in 1956. Mom always rode in the passenger seat, so I didn’t encounter the term until some of my contemporaries began driving (mid-seventies).
As an aside, if you’re Jason Mendoza, “shotgun” is the top of the hot air balloon that’s supposed to take you to heaven.
That took a little googling. And I watched the whole show, but don’t remember that part.
Google’s AI summary, for those who may also be wondering:
This refers to a classic, hilarious moment from the NBC comedy series The Good Place. When the demon Michael unveils a golden hot air balloon to transport the group, Jason immediately claims “Shotgun,” and upon being told that doesn’t apply to balloons, excitedly yells “Top of the balloon! Ultimate shotgun!”
It was just the front seat while I was growing up. I didn’t hear the term Shotgun until well into the 90s on various US TV shows, and I’m not sure I even figured out what it referred to from context until quite a few years after that.
Interesting item: on a stagecoach, where the term originated, the ‘shotgunner’ is seated to the left of the driver, who is on the right side (because that’s where the brake lever is).
But in most of the world, vehicles drive on the right side of the road, and drivers sit on the left front seat. So the right front seat is ‘shotgun’, the opposite of what it would be on a stagecoach.
Well, worth noting is that while it refers to the stagecoach era, it didn’t appear during the stagecoach era. Wiki says first reference is 1905, and it doesn’t start showing up in print until the 1920s.
The last true stagecoach runs (not for tourists, like at Knotts Berry farm) were at least until 1915, and maybe until the early 1930s. So, I’d say 1905 was in the last waning days of the stagecoach.
Excellent point. I remember one study that said that in some/many (I forget) crashes, unrestrained rear-seat passengers were safer than belted from passengers. This was before every car had 27 airbags, I’m sure.
And the “shotgun is most dangerous” I took to mean “other than the driver”, since the driver has no option as to where to sit. Well, except maybe for Ahh-noldt in Command where he ripped the driver’s seat out and drove from the back seat!
According to urban legend as tecounted by my mother, in the event of a head-on collision, the drive will attempt evasive action to save him/herself, so the “shotgun” position is more dangerous.
I have my doubts.
I first encountered the term in a book I read in the early 2000s, It wasn’t hard to deduce from context what it means but the origin of the term was a head-scratcher.
Certainly the driver has no choice of where to sit. While a single passenger could choose any of three seats in a generic sedan.
So it’s meaningful to rank those 3 passenger seats by average safety.
But I’m not sure whether you mean to say the driver’s seat is always the most dangerous, or whether you mean to say the relative danger of the drivers seat is simply irrelevant to both drivers and passengers, since each is stuck in their own category of seating.
The latter makes more sense to me, but your wording implies, at least to me, that you meant the former.
A fair question. I kinda mean both; iirc the driver is at highest risk by being on the oncoming traffic side and having a steering wheel in front of them. Otoh airbags may have changed that.
Well, in the days of the Old West the shotgun seat was clearly the most dangerous, since the bandits would be gunning for the guy with the shotgun 
Or may be not, because killing the driver first made escape more complex.
In the mid to late 90s in Scotland the term was known and used , well at least by people at work, although we had a lot of cross over and work trips to Houston so it was likely picked up there.
Another one I heard when we moved to the US ( west) was ‘riding cowboy’.
This refers to sitting in the middle seat of the front row of a truck ( with a bench seat at the front) . The source seems to come from field hands driving on country roads or ranch land where there were a lot of gates to open and close , the passenger sitting next to the door would have to keep jumping out to open and close gates , the smart cowboy would sit in the middle and not have to do anything.
I’d be careful about googling ‘riding cowboy’
In addition to the pillion position on a motorcycle, I have heard the middle seat in a pick-up as “riding bitch”, not cowboy. The cowboy reference could also be because in the middle position, you have to straddle the transmission tunnel, so your legs are kind of bowed.
“Riding bareback” is another unsafe-to-Google term. Although I bet more folks already know about that one than your contribution.
Pretty universal in the US, I think. My kid picked it up when he was 5 or 6, not sure from where.