Sorrel is a type of wild hibiscus (Hibiscus Sabdariffa). It's called a million different names all over the world, a few that include Jamaica and Roselle. I'm from the Caribbean and never knew until recently sorrel is a type of hibiscus - and I suspect a lot of other West Indians don't know this either. We just know it as sorrel - that delicious red drink that comes around at Christmas time.
Whether or not you add ginger has nothing to do with what makes 'sorrel', it's just a plant with a million different names that has origins all over the world, (and good news: it is being praised for having a lot of health benefits!)
For another recipe (from a West Indian who has never had Sorrel with ginger in it - but will give that a try! ):