[tyingq]

Well, given that the api does this:

  var popper = new Popper(referenceElement, onBottomPopper, {
    placement: 'bottom'
  });

Popper.js already knows that referenceElement is the association, so it seems reasonable to consider if it should (maybe optionally) create the <label> or aria association between the two.

Similar for default keybindings that make sense.

[FezVrasta]

I think this feature would be a perfect fit for a Popper.js plugin!