$(document).tooltip({

  open: function(e, ui) {

    //only the latter points to the element which I want to reference, but requires some workarounds in case of nested elements inside of an element that triggers the tooltip

    console.log(this, e.target, e.currentTarget, e.originalEvent.target);

    //this is what I'd like to get without this ugly workaround, the element that triggered the tooltip:

    var el = $(e.originalEvent.target || e.originalEvent.srcElement).closest($(this).tooltip('option', 'items'))[0];

    console.log(el);

    //alternative workaround

    console.log($('[aria-describedby="'+ui.tooltip[0].id+'"]')[0]);

  }

});

​