What is the expanded name of Windows Me?

Windows Me expanded to Windows Millennium Edition.

Microsoft released Windows Me in 2000 as the consumer successor to Windows 98. The “Me” abbreviation referred to “Millennium Edition,” matching the product's turn-of-the-millennium branding and its marketing focus on home users.

Windows Me was released to manufacturing on June 19, 2000, and reached retail stores on September 14, 2000. It introduced or bundled consumer-oriented features including Windows Movie Maker, System Restore, compressed-folder support for ZIP files, Internet Explorer 5.5, and Windows Media Player 7.

It was the final consumer Windows release based on the Windows 9x line and the last to rely on the MS-DOS foundation, although access to real-mode DOS was restricted. Windows XP replaced it in 2001 with the more stable Windows NT-based architecture. The other options confuse the name with unrelated Microsoft product terms such as Mobile, Media, or modular software concepts.