That Greek origin wasn't something my parents made up, I read it in an "etymology of names" book some 8 years ago, and as it was the only source I had found regarding it until few years ago I thought it was right. But maybe this one source was of that kind which use etymology unproperly. ;) Surely you know about this more than I do. Thanks for the info, really! You've settled my doubts since I've had that double origin thing in my mind for some time and I didn't know which one to believe, although the Greek one was more appealing to me since it was the first one I came across. :P I've been wrong for some few years, thanks for clarifying it to me.
Having that clear, it's only a question of bearing in mind that the Netherlands were very linked to Spain from the XIVth century to the modern era, so maybe here lies the reason why this name is also used in Spain. But again I might be wrong.