The folks at the Microsot has to think about the new name for the tile-based interface of windows 8 due to the trademark offence of the German retail giant "Metro AG" (However, I never heard the name before).
A Microsoft internal memo seen by The Verge indicates a discussion with a European firm prompted Microsoft to stop using the Metro name for its tile-based UI. Employees and developers have to adhere to the new Windows 8 style UI name immediately, the memo says.
The new metro UI was first implemented in the windows phone products, which was a popular interface of Microsoft's discontinued project -- Zune Media Player.
Microsoft denies the change is due to the trademark dispute, and explains in a statement:
"We have used Metro style as a code name during the product development cycle across many of our product lines. As we get closer to launch and transition from industry dialog to a broad consumer dialog we will use our commercial names."
It could be the Microsoft's preplanned theory to assign some catchy name for people to get used to it before the actual release for customers. They did the same previously when they were developing Windows Vista and Windows 7 (Longhorn and Blackcombs were used during the development phase but has then been changed to windows 7 and windows vista for commercial uses).