Oh yeah, I’d forgotten about the French, and it’s been a long time since my GCSE French lessons but wasn’t petit-déjeuner breakfast? Is that a more modern invention?
Any big main meal is dinner, regardless of when you have it. A meal in the middle of the day is lunch, a meal at the end of the day is tea, a meal shortly before bed is supper. Any of them can be dinner too, but they don't have to be.
Breakfast is breakfast though. Dinner for breakfast is not an option.