Back in the day, the noon/midday meal was called dinner also in the US. Particularly in rural areas.
And for some of us boomers it's still dinner. Growing up on a farm, Breakfast was 6am-ish thing after chores were done, (you could sneak in some jelly toast before chores if you weren't to lazy to get up early enough), the noon dinner, and you always came home to eat it, was a full meal deal because you had spent your morning often doing heavy manual labor. Plus your afternoon was going to be no different. You got lunch a 4pm because supper was a 7pm-ish meal, (often heavy on the "ish" part depending on what went wrong during the afternoon).
We evidently didn't get the memo about changing dinner to lunch until much, much later. Besides, we would have needed to rename "lunch" to something else for the 4pm break. I still call the noon meal dinner to this day. You can call it whatever you like, because I don't sweat those details.
