Extending the History of Words: The Case of "Ms."

Ms. is “used as a title preceding the surname of any woman regardless of her marital status, sometimes with her forename(s) intervening.” This is obviously a rather recent invention, compared to the title Mrs. for a married woman (from the late 15th century) and Miss for an unmarried woman (from the mid-17th century). But just how recent is it?
Extending the History of Words: The Case of "Ms."