Interestingly, the second person pronouns went the same way -- we dropped the second person singular in favor of using the second person plural exclusively. So

Interestingly, the second person pronouns went the same way -- we dropped the second person singular in favor of using the second person plural exclusively. So it's kind of amusing that people continually invent new second person plurals when, from a certain angle, that's the one we've got. I wonder if in another hundred years we'll be arguing about "they all" versus "thall".