Google loves to experiment with different features and UIs on its apps and services, and one of its favorite subjects is YouTube. Whether it's on the web or in its mobile apps, there always seems to be some new server-side change that's being tested. Today is no different; there are two name changes being tested in the Android app.
left: "Shared" and "Activity." right: "Messages" and "Inbox."
If this is all seeming a little familiar, you're not going crazy; that bottom tab has been renamed before (it went from "Shared" to "Activity"). At that time, the "Shared" name transferred to one of the two tabs up top. However, in this latest test, Google is now calling the bottom tab "Inbox," and the top tab "Messages." Both of these new names do seem a bit more fitting.
These names aren't rolling out to everyone; we've received two tips about it and I'm seeing it on one of my phones, but Artem isn't. To make things even more confusing, my other phone has the new "Messages" name, but not "Inbox." But of course, this is just another case of Google being Google.