Xenix was Microsoft's version of Unix intended for use on microcomputers; since Microsoft was not able to license the "UNIX" name itself, they gave it an original name. The -ix ending follows a convention used by many other Unix-like operating systems.
Microsoft purchased a license for Version 7 Unix from AT&T in 1979, and announced on August 25, 1980 that it would make it available for the 16-bit microcomputer market.
Xenix varied from its 7th Edition origins by incorporating elements from BSD, and soon possessed the most widely installed base of any Unix flavour due to the popularity of the inexpensive x86 processor.