Dont feel bad, thats one of those made up imaginary things that have become part of our story like pizza or spaghetti and meat sauce being Italian.
IIRC it goes something like, it was an English thing that European Jews were eating and began serving in East coast delis because Irish were poor. So it doesnt really have anything to do with Irish anyway.
At least in my lifetime JD was always crap for people more interested in adopting an image than actually drinking.
Luckily we have New Glarus here in Wisconsin.
No one gives a F about Budweiser/Anheiser Bush.