Christine Mallinson, associate professor of language, literacy, and culture, recently joined NPR’s “All Things Considered” for a discussion of the use of “yo” as a gender-neutral pronoun. Mallinson said that kids in Baltimore have solved a very old problem in linguistics: English doesn’t have a gender-neutral pronoun. That makes it difficult to refer to people if you don’t know the person’s gender. Youth in Baltimore often use “yo” instead of “he” or “she” when they don’t know a person’s gender. But they also use “yo” as a substitute even when they do know the gender. Mallinson, and other linguists, are …