You may as well say curry is curry because it has cumin in it, and cumin is native to India. Curry is really just a word made up by non-Indians to describe spicy gravy, or depending on who you ask, it can be used to describe any sufficiently spiced food. If you google curry potatoes, you’ll find plenty of recipes. If you google jeera aloo (which literally just translates to cumin potato) you’ll find plenty of very similar recipes. You can also find plenty of recipes for Thai, Indonesian, Malaysian... curries, and the only thing they have in common with Indian curries is use of spice and a gravy textured sauce, but using completely different spice bases and cooking techniques.
Not so. It's named after the Tamil word kari which means a dish eaten with rice and flavored with curry leaves (kari patta).