Hi Melissa, that is indeed a very interesting story. I took a quick look on the interent and there are a lot of "Bocanegras" around. When you want to research this, you could start with some of the geneology sites, for example the one at www.familysearch.org. If you know the name of the parents of your great grandmother, I'm sure this can take you much further back in time. There's some records of people with this name in spain around the 1300s.
Good luck and enjoy your research...