In contemporary New York City, it is common to hear local teenagers use the word “y’all.” A few decades ago, this word would have been confined to speakers of African American Vernacular English (AAVE), who brought the word with them from the American South. Yet nowadays, with the spread of AAVE, the word has been adopted by young New Yorkers of every ethnicity under the sun. But where did this strange little word come from? The answer reveals a remarkable (and unlikely) story of language dispersion. If you’re a little confused about what “y’all” means, you’re not alone. Even people who get the basic jist of “y’all” don’t grasp its grammatical purpose. The word is a “second person plural,” meaning it is a plural version of “you.” So, for example, in the American South (where “y’all” is most widespread) somebody would say: “You want to go to the store?” if they were talking to a single person. Or, “Y’all want to go to the store?” if they were talking to a group of people. How “...