Hello Elaine, I just see Your question in italki and I have one comment about it. Let me tell You when I read You question I have not Idea what's 'casco' means. I'm an Spanish native speaker and I'm from Lima-Peru, my country is located in South America. We never used that word to refer any place, here is different. I think this could help You. You know in my continent almost everyone speak Spanish, But sometimes in each country the people use different word to say the similar thing, and this create confusions. For example, I have a Venezuelan friend that when he try to say he is agree with me say 'eso' ... in English is like You say 'that' instead of 'Yes', 'of course'. Then when He told me the first time about him, his country and whatever, I'm asking him several times about words than I not understand. Finally, I think every country had their own way to said certain things. If sometimes is confused between native speakers, I imagined as hard this could be for foreigners. Greettings.