Was Minnie Mouse ever actually refered to by name in 1928

I know that Minnie Mouse appears in the 1928 Mickey Mouse cartoons, but was she ever referred to by name in any of them or any promotional material? I know Mickey's name is right there on the title cards, and I'm guessing the people at Disney probably had named Minnie at least within the production company, but was she ever actually refered to Minnie publicly during that time, or did that happen later? If she wasn't, does that mean her initial appearance may be public domain, but not her name?