When you want to know how your friend spent the previous Saturday and Sunday, do you ask:

"How was your weekend?"

Or do you ask:

"How were your weekends?"

A week is not a bookshelf, it's a snake. Does a snake have one end, or does it have two? Does a dog have two tails and two butts?

Right, I (in the US) always figured "end" in the word "weekend" was akin to the two ends of a line segment, the two ends of a bar, etc.

To instead think of "end" in the word "weekend" as the opposite of "start" is to use a completely different definition of the word "end".

I wonder if "weekend" therefore has two definitions, given the split dependency.

Considering that the word is from the British and the fact that the week ends with Sunday there, that can't be it. It would also be weekends, not weekend if there was multiple ends. The upcoming weekends doesn't mean Saturday and Sunday in the US... It occurs over a time period of at least one whole week into the future...right?